METAMORPHISM OF HYDROTHERMAL ALTERATION AT THE RED LAKE MINE, BALMERTOWN, ONTARIO

by

GI Clark Darner

A thesis submitted to the Department of Geo1ogical Sciences in conformity with the requirements for the degree of Master of Science

Queen' s University Kingston, Ontario, Canada July, 1997 copyright 8 0. Clark Damet National Library 8ibliiuenationale du Canada Acquisitions and Acquisitions et Bibliogtaphic Services services bibliographiques

The author has gmted a non- L'auteur a accord6 melicence non exclusive licence allowing the exclusive permetbmt a la National Library of Canada to Biblioth- nationale du Canada de reproduce, loan, distn'buie or sell repfoduire, p&k, distri'buetou copies of his/her thesis by any means vendre des copies de sa these de and in any form or format, making qyelqpe mmi&e et sous qpe1cpe this thesis avallsrblle to interested fome que ce soit pour mettre des persons. exemplaires de cette thha la disposition des personnes int&essCes.

The author retains ownership of the L'auteur coaserve la propriCt6 du copyright m hismet thesis. Neither &oit &auteur qyi prot&gesa th&se.Ni the thesis nor substantial extra& la these ni des extraits substantiels de fkom it may be printed or othemk ceJle-ci ne doivent &R imp1im6s ou reproduced with the author's autrement nppoduits sans son permission. autorisation. Frontispiece: The DeHavilland Norseman in downtown Red Lake. The Norseman was one of the first bush planes and played a major role in the Red Lake gold rush during the 1920's. Abstract The Rcd Lake Mine is a metamorphosed Archean gold deposit. It is located within the Red Lake greenstone belt of the Uchi Subprovin~in the northwestern portion of the Superior Province. Highly altered basaltic rocks in the Red Lake Mine have similar mineral assemblages to those observed in pelitic rocks. The highly altered rocks have Mered extensive premetamorphic hydrothermal alteration largely by the addition of K20, FeO and C* with almost the complete removal ofNa20. Blrllr rock CaO and A1203 are residually enriched. The maximum-phase mineral assemblages consists of: Grt+Bt+Chl+St+Cld+And+PL+Qtz+Ilm+Ank+Tm~Corn in altered rnetabasalts. The mineral assetnbleges preserved in the Red take Mine demonstrate that the transition fmm pellschist m amphibolite facies assemblages in weakly altered basaltic rocks occurs before the staumlitein isograd in highly altered basaltic rocks (essentially pelites) with alPll[ljllous assemblages. The low-variance mineral assemblages could have only arisen by the metamorphism of high-variance assemblages. Zoned hydmthemal alteration patterns have been preserved around ore-bearing zones. The "Main Zone" is enveloped by three minetalogically distinct maximum-phase mined assemblages: (1) Chl + P1+ Grt + And + Qtz + St + Cld + Bt + Ilm f Cum (Distal) (2) Hbl + Bt + Chl + P1+ Qtz + An.+ Mt + Dm f Ath (hermediate) (3)Bt+Ank+Qtz+Ms+Pl+Mtf Chl (Proximal) The zoning of mineral assemblages amund the "Main Zone'@at the Red Lake Mine represents metamorphism of hydrothermal alteration. The outer zone is inferred to have formed from a pmtolith rich in kaolinite (Le. a zone of advanced atgillic alteration). The intermediate zone may have formed from a chlorite-rich protolith (Lee a zone of intemediate argillic alteration or chloritization). Close to the ore-bearing structure, the proximal zone is inferred to have formed from a protolith rich in biotite, muscovite, quartz and ankerite (i-e. a zone of potassic alteration). During metamorphism, hydrothermal biotite, muscovite, chlorite, quark and ankerite are irrferred to have recrystallized and re-eqpilibrated with newly formed minerals such as garnet, staurolite and chloritoid while the lower temperature hydrothermal clay minerals in the outer zone were completely replaced by the newly formed minerals. Two hogcads have been mapped in the undetgtound workings of the Red Lake Mine: the staumlite-in isognd and the chloritoid-out isograd. The isograds strike approximately N2WE and dip 300Wwheceas the mine stratigraphy strikes approximately N45W and dips between 40-750W. Thetefore, isograds cross-cut the mine stratigraphy, alteration and ore zones, The low-variance mineral assemblages permit accurate definition of the P-'I' conditions of metamorphism. Two computer aided themobammetric programs were used to calculate pressures and temperatures: TWEEQU and WEBINVEQ, Pressures and temperatures vary systematically within the mine from 1400-2000 bars and 435- 48mwith TWEEQU and 1000-220 bars and 450-550% with WEBINVEQ. The PC% displays a systematic decrease with depth in the mine. P-T results indicate a very high geothermal gradient of about 70-900Cflrm. The high geothermal gradient is consistent with contact metamorphism by a nearby heat source (Lee the Walsh Lake Pluton) at depths between about 6-7 km. Acknowledgments

I would not have been able to complete this thesis if it wee not for the help of a great many people. First of all I wodd like to thank Dr. Dugald Cannichael who suggested this thesis topic and for giving me many valuable lessons along the way, both intellectual and financial as well as recreational. Your enthusiasm and sopport is greatly appreciated. I would also like to thank Goldcorp Inc. for allowing me access to their mine and for providing food and lodging while I was in Balmertown. The time I spent undergro~dwith Steve McGibbon, Tim Twomey, Dan Lemm and Steve Duenck is greatly appreciated. I would also like to thank Bob Chathaway for many interesting discwioas and for taking me golfing in Balmertown. Rob Penaak, now at Goldcorp Inc., provided many interesting discussions and was able to take time out of his busy schedule to collect some more samples for me. For this I owe you more than just a couple bars. I would also like to thank Tom Stubens and John Misiura of Placer Dome Canada Ltd. for giving me a tour of the Campbell Mine on such short notice. At Queen's University my educational experience was greatly enhanced by many of the professors especially, Dr. Alan H. Clark and Dr. Herb H. Helmstaedt I would also like to thank Dr. Bob Mason for many enlightening conversations on the geology of Archean gold deposits. Many other discussions on various aspects of the thesis with Dr. Doug A Archibald, Dr. C. lay Hodgson, Dr. Peter L. Roeder, Dr. Heather Jamison and Dr. John Hanes are greatly appreciated. A "HUGE BIG thanks goes out to all my Sends at Queen's especially those from the "Gro6e Namrwi~sentschaftler.~'Mike "Ooley"Cooley, "Newfie"Dave Gale and Gord Stretch have provided constant friendship from the beginning. I would also like to thank Tom Ulrich for his help with just about everything in the department from microscopes to computers. You should charge more for consulting fees. Most of all I would Wre to thank Rosalind Stephanian for her continued support and encouragement especially throughout this last year. You have proven to w that if someone can switch fkom German literature to geology that anything is possible. Du bist mein gold scisatz. This wok was financially supported by a Reinhardt Fellowship and a Queen's Graduate Award and by an NSERC research grant to Dr. DugaId M. Carmichael...... 1.1 General httodwtio...... 1 1.2 hvious wor k...... 4 1.3 Scope and Objectives of the Thesis......

2.1 Introduction...... 2.2 Supracrustal Assemblages...... 2.3 Intrusive Rocks...... 2.4 Geology of Balmer Township...... 2.5 Mine Geology ...... 2.6 Structural Geology, Alteration and Miaetalization ...... 2.7 Summary of Geo10gical Events ...... *......

3.1 Introduction...... 3.2 Mineral Assemblages ...... 3.2. 1 Sedimentary Rocks ...... 3.2.2 Ultramafic RQCkS...... 3.2.3 Felsic Extrusive Rocks...... 3.2.4 Felsic Intrusive Rocks ...... 3.2.6 Basaltic Ro& ...... 3.3 Garnet, ......

3.4 Ph@~~laseo~*e.*o.~**o~*~*~~*~~*~e*~~*e**~~m~***~~~~*~~~~~~m~*~~*~~~*mmm*a~~*~m~~o**-~~---*~me~~*~o~~~*~*~o-~~--~~~~v~ 3.5 Amphiboles ......

3.7 Chlorite......

3.13 Codentet ...... 3.14 Other Mined...... 3.15 Mineralogical Profile of the 'Main Zone" on the 34th Level...... 3.16 Significance of the transition fkom Chlodtoid- and Statxolite-bearing Assemblages ...... ~...... ~...... g....*...... e....o.*...... *...... 3.17 Discussion ...... g....*...... e....o.*...... *......

4.1 hfMduction...... ~...... 95 4.2 Analytical Methods ...... 98 4.3 Results of Thermoberometry...... 99 4.4 T-XC* Conhho-9 as ...... 120 4.5 Discussion ....g..e...... I2!5

APPENDIX 2 = MlCROPROBE DATA...... 151 List of Figures

Figure 1.1. Location map of the Red Lalre and the Uchi Subprovince ...... 2 Figure 1.2. Township map of Red Lake...... 3 Fip21. Genedhdmap of -tone belts in the Uchi Subprovince ...... 13 Figure2.2. Simpfifiedgeo108yoftbeRsd~~mtoaebelt...... 15 Figure 2.3. Stratigqhic subdivisions of the Rcd Lake greenstone by Pirie (198 1) ..... 16 Figate 2.4. Stratipphic subdivisions of the Red Lake gmenstone by Wallace et aL (1986) ...... 16 Figure 2.5. Tectonic assemblage map of the Red Lake greenstone belt by Stott and Corfi,(1991) ...... 18 Figrue 2.6. Geology map of Bialmer Towaship ...... 24 Figure 2.7. Complilation geology map of the 14th level of the Campbell Mine and the 15th level of the Red Lake Mine...... 28 Fipe2.8. Schematic cross-section of the Red take Mine ...... 29 Figure 3.1. ACF diagram of altered basaltic rocks in the Red Lake Mine...... 41 Figure 3.2. Graph of 2x10 versos apparent Na20 in EDS analyses of staurolite...... 73 Figure3.3. Mimra10gicalpcoNeoftbe'~Mainne"...... 84 Figure 3.4. Schematic cross-section of the Red Lake Mine with isograds...... *. 89 Figure 35. Geology map ofBalmerTowllship withisograds...... 90 Figure 3.6. Complilation geology map of the 14th level of the Campbell Mine and the 15th level of the Red Lake Mine with the staurolite-in isograd ..... 91 Figure 4.1. TWEEQU plot of sample 2413 with chloritoid ...... 101 Figure 4.2. TWEEQUand WEBINVEQplot of sample 15-017A...... 102 Figure 4.3. TWEEQU and WEBINVEQ plot of sample 28-886-2D ...... 105 Figure 4.4. TWEEQU and WEBINVEQ plot of sample 2e88.1 ...... 107 Figure 4.5. TWEEQU and WEBINVEQ plot of sample 3462364...... 109 Figure 4.6. Garnet - biotite thermometer of sample 9521-1 ...... 112 Figure 4.7. TWEEQU and WEBINVEQ plots of sample 2413 without chloritoid md with varying Xa20...... 113 Figure 4.8. Schematic cross-section of heRed Lake Mine with isograds and P-T vanahons...... 117 Figtm 4.9. Schematic petmgenetic grid of the "ideal"pelitic system with bathomnes...... ~...... 118 Figure 4.10. Petrogenetic grid from Spear and Cheney (1989) ...... 119 Figate 4.1 1. Sequence of TWEEQU plots of sunple 28-886-2D with

varying m20 m...... me -...... *...... *...... 121 Figure 4.12. T-Xq diagram illustrating the effects of P and X* on the stability of the banded quartz-te veins ...... 123 Figure 4.13. T-Xqdiagram frmn Chdstie (1986) ...... ,~.m...... ~...... ~...... s..s124 List of Plates

Phte 2.1 Pillowed tholciitc bdtsof the Bslmer Assemblage...... 19 Plate 22 Tightly folded sediments of the Bruce Channel Assemblnge...... 25 Plate 23 "Lamprophymn cmss-cutting the "SC" ore me...... 33 Plate 3.1A Two textural generatioas of chloritoid with sygmoidal inclusion trails...... 43 Plate 3.1B. Howglass structure in chloritoid ...... 43 Plate 3.2 Latetectonic mddasite~~.m~e~~~~~~~~~mm~a~~m~~~~e~~~~~~~e~~~~L8.~~~e~.~C~~~**~~~~~~~O~~e*.~~**m*~~~~~~ 49 Platc3.3 Lngepoikiloblastofcordieritewithzinciaasta11lolitehclUSio~~...... 49 PUe 3.4 Blue quartz "eyes" in the "CampbelyDickensondiorite" ...... 50 Plate 3.5 kuartz in the "CampbelyDickensondiorite" ...... 50 Plate 3.6 Garnet porphymbest in a QFP...... e...... 53 Plate 3.7 Garnet with ab~dantinclusions of arsenopyrite. pyrite and magnetite...... 58 Plate 3 .8 Late-tectonic garnet porphyroblast with biotite and plapioclase ...... 58 Plate 3.9 Cdcic plagioclase with conspicom radial extinction...... 62 Plate 3.10 Calcic plagiochse with yellow-geen cathodolumiuescence ...... 62 Plate 3.1 1 Clunmingtonite inclusions in gamet ...... 65 Plate 3.12 Magnesia-hornblende in the matrix of a cockade breccia...... 65 Plate 3.13 Radiating anthophyllite in a vein ...... 70 Plate 3.14 Biotite intergrown with chlorite ...... 70 Plate 3.15 Latetectonic stamlite and chloritoid porphyrob lasts...... 76 Plate 3.16 Ephedral mdalusite porphyrobhts in a deformed quartz vein ...... 76 Plate 3.17A Matgarite in metasediment with muscovite...... 79 Plate 3.17B Cmndated margarite in metasediment with muscovite end andalusite...... 79 Plate 3.18 Rumortierite with biotite in the East South "C" ore zone...... 82 Plate 3. 19 Dunortierite with biotite and stawlite fiom the South "C" ore zone...... 82 Plate 3.20 Layer of garnet and cumrningtonite from the distal alteration zone ...... 85 Plate 3.21 Ptygmatic vein with staurolite. chloritoid. plegioclase. and andalusite hmthe distal alteration zone...... 85 Plate 3.22 Magnesio - hornblende and anthophyllite in the intermediate alteration zone ...... 87 Plate 3.23 Equigranulat intergrowth of biotite. ankerite, quartz, arsenopyrite. pyrite and magnetite from the proximal alteration zone...... 87 List of Tables

Tabk L Mineral abbreviations and f~l~lPlae...... viii Table 1.1 Gold production in Red ...... 5 Table 2.1 Rock types in the Campbell-Red Lake Mine Canpkx...... 27 Table 22 Smnmsry of geological events in the Campbell-Red Lake Mine Complex... 38 Table 3.1 Mineral assembIages in mcmnts...... 45 Table 33Mineral assemblages in altered Plttamafic mdw ...... 45 Table 3.3 Mineral assemblages in "Rbyolitea'...... 48 Table 3.4 Mined assemblages in 'PiOtite...... 48 Table 35Mined assemblages in dyke rocLs...... 52 Table 3.6 Mined assemblages in altened basaltic sks...... 55 Table 3.7 Microprobe dyses of garnet ...... 59 Table 3.8 Micropbe analyses of plagioclase ...... 61 Table 3.9 Microprobe analyses of mpbibole...... 64 Table 3.10 Microprobe analyses of biotite ...... m...... 68 Table 3.11 Micropbe analyses of chlorite*...... 69 Table 3.12 Microprobe analyses of stamlib...... 72 Table 3.13 Microprobe analyses of chloritoid. andalpsite. cordierite. muscovite and matgarite...... 80 Table 4.1 Solution models and activities used in thermodynamic calculatioas ...... 98 Table 4.2 Four independent reactions in the assemblage Grt+Bt+Chl+Pl+And+St+Qtz ...... m...... 100 Table 4.3 Average mimpmbe analyses of minerals in 15417A...... 103 Table 4.4 Avenge microprobe analyses of minerals in 28-88 62D...... 106 Table 4.5 Average micropbe analyses of minerals in 24-88-1...... 108 Table 4.6 Tbree independent mctions in the assemblage Crd + P1+ St + Bt + ChL + Ms + Mrg + And + Qlz ...... 111 Table 4.7 Average mh~~p~beanalyses of minerals in 34L-236.1 ...... 110 Table4.8Avengemi~t0ptobeandysesofrnindin9521~1...... 114 Table4.9Avemgemicmpmbeanalysesofmirreralsin2413...... m...... 115 Table 4.10 Summary of P-T-Xcq conditions with TWEEQU.m~.m.--b-mm-.L~e~m~me~~me*--~-~ma122 Table A-1 Petrography of samples fnna sorfixe to the 17fh level ...... 147 Table A-2 Petrography of samples from 23d to the 28th leveL ...... 148 Table B 1. Microprobe analyses of gsmct fran 9521.1 ...... 152 Table B2. Microprobe analyses of biotite 6mm9521-1 ...... 153 Tabk B3. Micropcob analyses of chlorite from 9521-1 ...... 154 Table B4. Micmpmbe analyses ofpllgiaclase fkm 9521.1 ...... 155 Table B5a. Mictoptobe analyses of amphibole fmm 9521.1 ...... 156 Table BSb .Mimprobe analyses of ampbibole from 9521-1 ...... 157 Table BSc .Mimprok analyses of amphibole finm 9521-1...... 158 Table B6a Microprobe analyses of ilmenite from 9521-1 ...... 159 Table B6b .Microprobe analyses of ilmenite from 9521-1 ...... 160 Table B7. Microprobe analyses of &rite fmn 9521-1 ...... 161 Table B8 .Mimprobe analyses of gamet hrn15417k ...... 162 Table B9 .Microptobe analyses of biotite from 15417A...... 163 Table B10. Micropbe analyses of chloate fmm 15417k...... 164 TableB11. Microprobeanalyses of plagioclasefrnn 15-017A ...... 165 Table B12. Microprobe analyses of stamlite from 15417A...... 166 Table B 13. Microprobe analyses of andalasite fiom 15-017A...... 167 Table B14. Microprobe analyses of magnetite Emm 15417A...... 168 Table B1S. Microprobe analyses of ilmenite from 15417A...... 169 Table I316 .Microprobe analyses of garnet from 24-88-1 ...... 170 Table B17. Microprobe analyses of biotite fbm 24-88-1 ...... *...... *.****..*** 171 Table B18. Microprobe analyses of chlorite from 24-88-1 ...... *.*...... 172 TableB19. Mi~t0probeandysesofpla~0~lasefrom2688-1 ...... 173 Table B20. Microprobe analyses of cbloritoid fmm 24-88-1 ...... 174 Table B21. Microprobe analyses of staurolite fmm 24-88-1 ...... 175 TableB22Mi~t0pn,bedysesofilrnenitefrom15.O17A...... 176 Table B23. Microprobe dysesof garnet from 2413...... *...... **.*...... 177 Table B24 .Microprobe analyses of biotite from 2413 ...... 178 Table B25 .Micropbe analyses of chlorite fhn2413 ...... 179 Table B26 .Microprobe analyses of plagioclase from 2413 ...... 180 Table B27 .Microprobe analyses of chloritoid from 2413 ...... 18 1 Table B28 .Microprobe analyses of statuolite from 2413...... 182 Table B29 .Microprobe analyses of ilmenite fnrm 2413 ...... 183 TableB30.MimprobeanalysesofgarnetErom26~917A...... 184 Table B3 1. Microprobe analyses of amphibole and biotite from 26-9 17A...... 185 Table B32 .Microprobe analyses of plapioclase frnn 2413 ...... *.*...... *.*.**...**.. 186 Table B33 .Microprobe analyses of garnet from 28-886-2D...... 187 Table B34. Micropbe analyses of biotite fmm 28-886-2D...... 188 Table B35. Micmprobe analyses of cblodte fkom 28.884-rn ...... 189 Table B36a. Micmpmbe aaalyses d plagioclase fmm 28-886-2D., ...... 190 Table B36b .Microprobe analyses of pIagiocIase Zrom 28-88 62D...... o...... o.w...191 Table B37 .Mictopbe analyses of stamlite from 28-886-2D...... 192 Table B38. Mictoptobe analyses of andalpsite from 28.886 2D...... 193 Table B39 .Mictoprobe analyses of magnetite fmn 28-8862D...... 194 Table L Table of mineral abbreviations used in the thesis with their associated mineral names and chemical formttlas used to cahbte activities. Mineral abbreviations aAer KLerz (1983) with modifications fa mvlepsented miacrsls.

Ab albite

catcitc chhite cbloritoid dcritc fmmhgmitc diopside dolamite fimumhite cpi- w== @rite grutreri* homblaldc antali feldspar kyanite m=@tc magnetite muscovite -'bole WroPbym* PblOPPite eLasi-l= '3- nrtile sc~polite scb#litt sta\nolite L!ilbmdtc spiatI talc titauitc taonaaliac tmnolite vcsuvianite zkoa 1. Introduction

1.1 General Statement

The Red Lake Greenstone Belt (rux3B)is located in the Uchi Subprovince of the Archean Superior Province in northwestern Ontario (Figure 1-1). The only curzently producing mines in the area are the Campbell Mine owaed and operated by Placer Dome Canada Ltd and the Red Lake Mine owned and operated by Goldcorp hc. The Madsen Mine will reopen in the summer of 1997. The mines have adjoining leases and are located in Baher Township, near Balmertoum, Ontario (Figwe 1-2), 275 km northwest of Thunder Bay. The two mines exploit the same gold-bearing system and they will heteafter be referred to as the Campbell - Red Lake Mine Complex (CRLMC). The Rod MeMine (formerly known as the Dickenson mine and the A. W. White mine) was initially staked in the Red Lake gold rush of 1926. However, no significant discoveries we= made and the claims were dowed to lapse. The ground was restaked in 1944 and eventually caught the attention of John U Brewis and Arthur W. White of Brewis and White Limited who financed new diamond drilling and later incorporated Dickenson Mines Limited. Diamond drilling commenced in March, 1945. Afw a number of promising, but erratic drill-hole intersectio11~the decision was made on July 10,1946 to sink an exploration shaft. Initial milling began in 1948 at rate of 125 tons per day. In 1978 Dickenson Mines took over the adjoining Robin Red Lake Mines Limited property and the two companies were merged. In the early eighties, due to decrrasing reserves and the falling price of gold the company was in serious finand trouble. Howevet, after some resctacturing, fdlowed by a rise in the price of gold and recent exploration success the company, now Goldcorp Inc., appears to well established for the hture. The ground on which the adjacent Campbell Mine now sits was originally staked by George W. Campbell and Colin A. Campbell. Campbell Red Lake Mines was Figure 1-1. Map showing location of Red Lake and the Uchi Subprovince within the Superior Province. Geological subdivisions after Card and Ciesielski (1986). Figure 1-2. Townships of the Red Lake Greenstone Belt incorporated in July, 1944 and the property was later optioned to Brewis and White Limited (Chisholm 1951). The pmpezty was then re-optioned to Dome Exploration (Canada) Limited and has been in continuo^^ podaction sina 1949. The mine is currently owned and operated by Placer Dome Canada Ltd. The Red Lake mining camp has been an important gold producer since 1930 and ranks third in gold production in Canada following only the plific Timmias-Porcupine and Kiddaad Lake gold mining camps. The Campbell Mine and the adjacent Red Lake Mine are the largest and only current producers in the district. The majority of the gold has been pmduced by the Campbell Red Lake Mine flable 1-1). The Campbell Red Lake Mine has produced over 8.5 million ounces of gold since 1949 and has pmven and probable reserves as of Decembrr 3 1, 1995 of 4,495,000 tons at 18.0 glt (0.58 ouncedton) with 2,607,000 ounces (81,083 kg) of contained gold (Placer Dome k, Annual Report 1995). The Red Lake Miae has produced over 3.1 million ounces of gold since 1948 and has proven and probable reserves as of December 31, 1995 of 3,700,000 tons at 13.7 g/t (0.44 ouncesltoa) with 1,633,000 ounces (50,790 kg) of contained gold (Goldcocp Inc., Annual Report, 1995). Recently, Goldcocp Inc. has added substantial new proven and probable reserves of 1,800,000 tons of "low grade" ore at 8.6 glt (0.25 ounces/ton) as well as 1,000,000 tons of "high grade" orp at 41 g/t (1.3 wnces/ton) (Northern Miner, Sept. 23,1996).

1.2 Previous Work

The first geological investigation carried out in the Red Lake disrrift was by Dowling (1894) of the Geological Survey of Canada in the summer of 1893. Dowling reported dolomitic limestones with associated greenstones and quartz feldspar dykes. These findings were later followed up by Bruce (1924) of the Ontario Department of Mines who was sent to Red Lake to produce a reco~aissancemap to investigate the findings of local pmspectors. He found out that the dolomitic limestones reported by Table I- 1. Red Lake gold production, April 2, 1930 to December 3 1,1994. From Atkinson and Storey (1995).

duced Grade Mine Yeam of Production Ore Miiied Kilognms Ounces IOrarns [Short Tons) Per Ton Per Ton Howey 4 630 779 13 113 0,091 (2) 3,35 McKenzie Red Lake 2 353 833 Red Summit 59 1 Red Lake Gold Shore 86 333 Gold Eagle 180 095 Madsen (3) 8 371 631 Hasaga 1 515 282 Cochenour-Willans (4) 2311 165 McMamac 152 978 Red Lake Mine (5) 7 973 796 Starratt Olsen 907 813 Campbell 14 030 655 H.G. Young 288 179 Mount Jamie 552 Buffalo 31 986 Abino 2 733 Lake Rowan 1986-1988 13 023 Total

Noscs: (1) Continous prududion fmm 1930-1941: lacludoa 268 ounces fmm clean-up ia 1937, (2) Fmm 1930.1941 the ora mined at Howcy bcfom sorting mUcd 5 158 376 mas. The avenge producdoa fiam runsf-mine om lhcrcfocc 0.0817 ouaccr per ton (2.80 gh), (3) Sea to ms(ut produdion in l!W/l!W8, (4) Inclwks pnducdon from the Annco mb WUmu pcopcdor, (5) tnclu&s pauductioa fmm the Robin Red Irke my, Dowling were not in fact sedimentary carbonates, but carbonate replacement umes in rnafic volcanic mcks. Following the discovery of more gold in the area Bmce and Hnwley (1927) as well as Hunt (1935) were sent to twsmnhe the geology in light of the latest discoveries. Starting in 1937, the area was then extensively mapped by Hocwood (1940) who also produced a large volme on the geology and ore deposits of the Red Lake area. Numerous theses were carried out in conjunction with Homood under the supervision of Bmce at Qgeeds University including Mdjill(1939), Gummer (1939). Codord (I-), Hoiles (1941), and Martison (1942). Later mapping focused on the townshipscale geology. Chisholm (1951) stadied the geology and mineral occurrences of Balmer Township. Ferguson (1962,1965,1966, 1968) mapped Bateman, Baird, Dome and Heyson Townships. Ferguson's work was followed up by Riley (1969,1972,1975a, 197!%, 1975c, 1976,1978a, 1978b) who carried out more detailed mapping of Ball, Mdcahy, Todd, and Fairlee Township. Pirie and others mapped the eastern side of the greenstone belt between 1976 and 1979 including Graves and McDonough (Pirie and Sawitzky 1977% 1977b). Bateman and Balmer (Pirie and Giant, 1978%1978b), Byshe, Ranger and Willam (Pirie and Kita, 1979~1979b, 197%) Townships.

Further work by the Ontario Geological Swey in the 1980's and the early 1990's included both regional and detailed studies on variotw aspects of the geology in the Red Lake district. Regional stratigraphic studies were done by Pirie (198 1,1982), Wallace et al. (1986) and Stott and Codb (1991). Radiometric dating using U-Pb techniques in zircon was carried out by Codk and Wallace (1986), Cocfb and Andrews (1987) and Noble et rrL (1989). Ar-At geocbronology was carried out by Wright and York (1990) and Yo& et al. (1991). Regional and detailed stratigraphic and struchual studies (Berger 1984; Berger and Helmstaedt 1984; Berger and Summers 1983,1984; Hugon 1984; Sanborn 1983,1984; and Wilson et al. 1984) were carried out with varying emphasis on gold mineralization. Multidisciplinary studies (Andrews 1982,1983,1984; Andrews and Wallace, 1983; Andrews et aL 1986, Durocher and Bwchell1983; Dmxher and Hugon 1983; Dorocher and van Haaften 1982) emphasized the characteristics and controls on

gold minecaIization of various deposits. Hugon and Schwerdtner (1985) were the first to suggest that the Red Lake Greenstme Belt is transected by a conjugate set of regional scale defonnation zones, Recent geo10gic maps produced by the Ontario Geological Survey include Baird (Wallace and Atkinson 1993), Dome (Atkinson 1993a) and Heyson (Atkinson 1993b. 1993c) Townships and the northeast corner of the Red Lake Greenstone Belt (Atkinson and Stone 1993). Dorocher et al. (1991) have produced a map of the entire Red Lake district showing the distribution of known gold showings. Other studies in the Red Lake district include palwmagnetcs (Constanzo-Alvarez and Dunlop 1993). lead isotopes (Gulson et al. 1993) and fluid inclusions (Lalcind 1984; Lakind and Brown 1984). Paleomagnetic studies conclude that the altered, mineralized and deformed rocks in the CRLMC have a different remnant magnetization than surrounding unaltered rocks. Lead isotopes are too variable to be of any use in determining the origin of the gold Fluid inclusion studies by LaLind (1984) and Lakind and Brown (1984) concluded that the primary (gold-related) fluid inclusions are low salinity with high C% contents and homogenization temperatures of 1lO-3dOoC. Studies specific to the Campbell - Red Lake Mine complex began almost with the onset of production with Holbroolce (1949). Chisholm (1951) and Jarvis (1953). After a long hiatus Ferguson et aI. (1972) gave a brief description on the geology of the

Campbell Mine. A number of studies we- initiated at Queen's University in the early 1980's after Hodgson and Helmstaedt (1979). The relationships between structure and gold minecabation in the CRLMC have been addressed by Rigg (1980) and Rigg and Helmstaedt (1981); Hodgson et aL(1980); Hodgson and MacGeehan (1981); MacGeehan and Hodgson (198 1,1982); MacGeehan et al. (1982); Andrews and Hugon (1985) and Christie (1986). Rigg (1980) and Rigg and Helmstaedt (198 1) concluded that all the ore zones are epigenetic and C~OSS-CU~the supracrustal rocks except for possible syngenetic mimralization in the ESC (East South C)ore zones. They also suggested that the source of the gold-bearing fluids was the metamorphic out-gassing of rocla passing through the greenschist-mphibolite facies bransition at depth. Hodgson et aL (1980), Hodpn and MacGeeban (1981). MacGeehan and Hdgson (1981,1982). MacGeehan et aL (1982) devised a compIicated multistage process for alteration, mineralization and metamorphism including pn- syn- and post-metamorphic hydrothermal alteration and mineralization. MacGeehan and Hodgson (1980) were also the fiRt to recognize that the "banded carbonatechert" veins formed in a near sprfiace environment (4km). However, they could not explain the fact that the host mcks apparently bad textures indicating they had fonned at considerable depth (5-10 km). Numemos studies followed on the ESC onzones because of its possible syngenetic origin. Mathieson (1982) and Mathieson and Hodgson (1984) have studied the nature of alteration, mineralization and metamorphism of the ESC ore zone at the Red Lake Mine (see below). Kusmhski and Crocket (1980), Cowan and Crocket (1980) and Crocbt et aL (1981) concluded that gold may have originally been syngenetic and was concentrated during defomation and metamocphism. Cmcket and Lavigne (1984), Lavigne and Crocket (1982,1983), and Lavigne (1983) focused on the geological setting of the ESC ore zone by looking at the gold content and sulphur isotopes in the ore zone and interflow metasediments. Kerrich et al. (1981) also studied the geochemistry of interflow metasediments in the Red Lake Mine. Rogers (1992) studied the geological setting of the Red Lake Mine with respect to grade control. 2hang et aL (1995) have started structural work at the Campbell Mine. This study is still in progress. Other studies still in progress ace associated with the multidisciplinary Western Superior LITHOPROBE transect which was initiated in 1995. Studies that have discussed metamorphism in the Red Lake district include Thurston and Brealrs (1978), Pirie (1980), Mathieson (1982), Mathieson and Hodgson (1984), Andxews and Wallace (1983). Andrews (1984). Andrews and Hugon (1985). Andnws et al. (1986), Lavigne (1983) and Lavigae et aL (1988, Christie (1986). Corfu and Andrews (1987), Colvine (1988), Stott and Cofi (1991), Tat~locaiand Hattori (1994) and Penczak (1996). Although, there appears to have been numerous studies done on the conditions of metamorphism, this is not the case. Thurston and Breaks (1978) conc1uded that the Uchi Subpmvince is characterized by low pressure subgreenschist to greenschist facies metamorphism. More specifically, the Red Lake Greenstone Belt is characterized by a vast central axes of low grade metamorphism with undivided medium-high grade metamorphism mtticted to areas proximal to the major plutws, Pirie (1980), Andrews and Wallace (1983) and AadRws (1984) placed the greenschist-amphibolite facies transition 2-3 hn from and parallel to the Tmut Lake batholith. Based on apparent changes in grain size, amphibole textures, carbonate occurrence and the presence of aluminosilicate minerals Andrews and Hugon (1985).

Andrews et. a1 (1986) and Colvine (1988) have suggested that the CRLMC is intersected by the pnschist-amphibolite facie isograd. They suggest that this isograd had major controls on the style of minecalkation and that alteration, metamorphism and mineralization were contemporaneous with the intrusion of the Trout Lake batholith. Lavigne (1983) and Lavigne et al. (1986) concluded that alteration and mineralization were coincident with defonnati011 and presumably, metamorphism. Mathieson (1982), Mathieson and Hodgson (1984) and Christie (1986) concIuded that alteration was pre- andlor syn-metamorphic. However, they state that hydrotherxnal alteration was not related to gold mineralization and that gold mineralization occurred during metamorphism. Mathieson (1982), Mathieson and Hodgson (1984) and Christie (1986) used arsenopyrite thermometry to quantify the temperature at which arsenopydte equilibrated with pyrite and pyrrhotite. They also utilized schematic pewgenetic grids based on mineral assemblages thought to be in equilibrium without taling into account various minerals (i.e. plagioclase and chloritoid) and their chemistry. They concluded that the cocks in the CRLMC equilibrated at pressures and temperatures between 34 kbars and 410-5e, zle~pectively.Christie (1986) took this one step further and used T-XC* diagams to constrain the fluid canpsition between 0.3 and 0.55 XC%. Apart from these two separate temperatares obtained wing sulphide thermometry no one has attempted to quantify the pnwmes and temperatures at wbich the rocks in the CRLMC equilibrated during metamorphism. Controversy remains over the relative thing of hydrothermal alteration, gold mineralization, deformation and metamorphism. Recently Pen& and Mason (1995% 199%. 1995c) and Fend(1996) have studied the origin and geological context of alteration and gold mineralization in the CRLMC. They conclude that all hydrothermal alteration and associated gold miaeraIization occtlrred prior to regional deformation and metamorphism. Pen& (1996) states that the CRLMC is a "metamorphosed epithemal gold deposit and the zoned alOminous alteration, open-space filling textures of main stage veins and vein breccias, multiple phases of hydrothermal braxias, anomalous Au-Ag-As- Sb-Hg-Zn-K are similar characteristics to those of recent low sdphidation epithennal deposits." Tarnocai and Hattori (1994) have also studied various aspects of hydrothermal alteration, gold mineralization and metamorphism. However, they conclude that auriferous hydrothermal activity and associated alteration began prior to peak metamorphism and continued after peak metamorphism.

1.3 Scope and Objectives of the Thesis Due to numerous low variance silicate-carbonate mineral assemblages (Mathieson 1982). the rocks in the CRLMC offer an excellent opportunity to apply thennodynamic constraints to an Archean lode gold deposit to test whether equilibrium was closely approached and to quantify the P-T-X coaditions of metamorphism. This wiU be achieved by documenting the nature and distribution of diagnostic mineral assemblages dvoughout the CRLMC using strict thin section petrography. Mineral chemistry will be documented using an electron rnimpmbe. Fiially, thermodynamic conditions will be quantified Psing the above data and the computer assisted themobammetric techniques of Berman (1991) and Gotdon (1992). With tbis information a clearer picture of the pressure, temperature and XC% of metamorphism Regional and Mine Geology

21Introduction

The Uchi Subprovince, which hosts the Red Lake Greenstone Belt (RLGB), is located in the western part of the Superior Province in northwestern Ontario, Canada (Figure 1-1). It is bounded to the south by the English River Subpmvince via the Sydney We- St Joseph Fault system and grades to the north into the Berens River Subprovince (Figure 2-I), a plutonic belt consisting of gneissic tonalites. The English River Subpmvince is a high grade metasedimentary - plutonic belt that is very similar to the Quetico Subpmvince (Breaks 1991). The UchI Subprovince is not unique among granite - greenstone tecranes in the Archean. It consists of linear belts of volcanic, sedimentary and syn-volcanic intrusions which were intruded by younger plutoas and batholithic complexes. Regional subprovince relationships have been used to subdivide the tectonic evolution of the Uchi Subprovince into three stages (Stott and Corfa 199 1). The noahem pacts of the Uchi Subprovince and the older (>2800Ma) parts of the Red Lake Greenstone Belt are interpreted as being parts of a rnicmcontinent comprising the North Caribou temeagainst which subsequent younger terranes collided (Stott and Coefp 1991). The amalgamation of parts of the Berens River, Uchi and Sachigo Subprovinces as well as the Pickle termne to fonn the North Caribou terrane represents the fint stage of accretionary growth. The second stage is represented by a period of crustal growth and deformation that encompassed the whole subprovince and involved magmatism along a southern convergent continental margin. This convergent margin is likened to the Cretaceous island arc-marginal basin complex, the "Rocas Verdes" in southern Chile

(Tamey et & 1976) by Stott and Corfu (1991). Subduction manifested itself during this period when the North Caribou micro-continent overrode subducted oceanic crust until it collided with another micro-continent fmn the south. The English River Subpmvince has been interpreted to have famed as a fore-arc accretionary prism within this subduction prism (Lansford and Morin. 1976). The fial tectonic stage involved micro- continent coUision from the south (the Wdpeg River-Wabigooa Superterrane) during the Kenoran orogeny. This final collision mpresents one phase of the supextemme accretionary event that led to the construction of a large stable craton: the Superior Province.

2.2 Supracrustd Assemblages The Red Lake Gnenstone Belt (RLGB)is a typical Archean greenstone belt composed of mainly mafic volcanic rocks with lesser amounts of felsic volcanic rocks, clastic sedimentary rocks (Le. turbidites) and local iron formation bounded by felsic intrusive rocks of the tonalite - trondhjemite - granodiorite WG)suite (Figure 2-2). The supracrustal sequence within the RLGB represents at least 270 million years of volcanism and sedimentation from 3000 Ma to 2730 Ma separated by discrete episodes of erosion and magmatism prior to the intrusions of the surrounding batholiths (Corfu and Ankws, 1987). Metamorphism in the Uchi Subpmvince is for the most part low grade, with medium - high grades generally restricted to the boundaries of the major plutons (Thurston and Breaks, 1978). The RLGB was originally subdivided by Pirie (1981) into a Lower Mafic Sequence composed of tholeiitic to komatiitic flows which occupy the central portion of the belt and Uuce calc-alkaline sequences, the Graves, Ball and Heyson sequences, which summd the central portion of the belt on the north, west and south, respectively (Figure 2-3). Later work by Wallace et al. (1986) grouped the four sequences of Pirie (1981) into three volcanic cycles, Cycle I, 11 and III (Figure 2-4). Corfu and Andrews (1987) refined the three cycles of Wallace et aL (1986) after subsequent U-Pb geochronology

Figure 2-3. Stratigraphic subdivisions of the Red Lake gwnstone belt by Pirie (198 1). Cucles and triangles denote gold deposits.

Figure 24. Stratigraphic subdivisions of the Red Lake greenstone belt from Wallace et al. (1986). into the lower, middle and upper sequences which mughly comspond to Cycles I, II and IIT. The RLGB has most mntly been subdivided into five distinct volcan~~~entary assemblages by Stott and Codb (1991) based on the earlier regional stratigraphic work of

Pirie (1981). Wallace et aL (1986), Corfu and Wallace (1986) and Codp and Andrews (1987). Stott and COWS(1991) assemblages include from 01dest to youngest: the Balmer Assemblage, BdAssemblage, Brace Channel Assemblage, Woman Assemblage and the Confederation Assemblage Figure 2-5). The Balmer Assemblage, which hosts the major gold deposits of the area including the Campbell - Red Lake Mine Complex, is the oldest and most widespread of the five assemblages in the RLOB. The Balmer Assemblage cornsponds to the Lower Mafic Sequence of We (1981) and Cycle I of Wallace et aL (1986). This assemblage form the central core of the RLGB owing to its general anticliaal configuration. The rocks are predotairlantly thoIeiitic basalts and komatiitic lava flows with lesser amounts of oxide imn formation and felsic volcanics that range in age fmm 2992 to 2958 Ma (Corfu and Wallace 1986 and Codu and Andrews 1987). The tholeiitic basalts are commonly pillowed (Plate 2-1). The BaImer Assemblage has been interpreted to have formed in a local shallow marine environment dominated by oceanic volcanism (Stott and CorfD 199 1). The BaIl Assemblage outcrops in the northwestern comer of the RLGB. It is equivalent to the main part of the Ball Calc-Alkaline Sequence of We (1981) and Cycle II of Wallace et al. (1986). This assemblage is composed predominantly of calc-alkaline m&c volcanics interbedded with intermediate to felsic pyroflastic rocks. Dolomitic marble and chert occur near the stratigraphic top of the sequence with minor oxide iron formation. The carbonate beds contain some of the best preserved strornatolites in the Superior Province (Hoffman et aL 1985). U-Pb geochronology in zircons from felsic volcanics below and above the carbonate units have been dated at 294022 and 292!5&3 Ma, respectively (Corfu and Wallace 1986). The Ball Assemblage is believed to be in

Plate 2-1. Outcrop of pillowed tholeiitic basalts of the BaJmer Assemblage near East Bay. Pillows face to the top of the photograph. Photograph taken looking northeast. fault contact with the older Balmer Assemblage (Stott and Coda 1991). The interpreted environment for the formation of the Ball Assemblage includes both subaerial and

subaqueous arc volcanism with local shallow submarine shelf-type carboaptes (Stott and Corh 1991). The Bruce Channel Assemblage outcrops on the eastern side of the RLGB. It is poorly exposed and consists pdornin~~~tlyof basaltic flows capped by minor mounts of felsic pymclastic rocks, clastic scdimeatary rocks and iron formation. The feMc volcanics have been dated at 2894 Ma (Cob and Wallace 1986, Corfa and Andrews 1987). The highly folded nature of the eastern part of the RLGB is accentuated by the sedimentary units of the upper Bruce Channel assemblage in the vicinity of the CRLMC. The Bruce Channel Assemblage tectonically underlies the older Balrner Assemblage and is fault contact with the Confederation Assemblage to the south. The contact with the Woman Assemblage is unknown, but may possibly be unconfonnable. Bimodal volcanism with associated sediments is interpreted to have fomed as a nsdt of island arc volcanism (Stott and Corh 199 1). Although the Woman Assemblage is widely distributed throughout the Uchi

Subprovince, it is represented by only one OUUXO~of 2830 Ma felsic volcanics on MacKenzie Island in the central portion of the belt (Corfu and Wallace 1986). Its relationship with the Baher and Bruce Channel Assemblages is clnknown due to the fact that its contacts are under the waters of Red Lake. It is intruded by the 27 18 & 1 Ma Dome stock (Co& and Andrews 1987). The Woman Assemblage is also interpreted to have formed in response to island arc volcanism (Stott and Cork 1991). The Confederation Assemblage is the most dominant volcanic assemblage in the Uchi Subprovince. In the RLGB it is equivalent to the Heyson and Graves Calc-Alkaline Sequences of Pirie (1981) and Cycle III of Wallace et al. (1986). It is composed chiefly of rhyolitic pyroclastic deposits interbedded with minor amounts of intermediate volcanics and underlain by tholeiitic to calc-alkaline mafic volcanics. This assemblage ranges in age from 2750-2730 Mo comsponding to the most extensive peaof volcanic activity in the Superior Pmvince (Stotr and Coefu 1991). The Confederation Assemblage is in fault contact with the Baher and Brace Channel Assemblages. The 27182 1 Ma Dome stock cross-cuts the contact between the Balmer and Confederation Assemblages. The Confederation Assemblage is also inapmted to have fodin an island arc environment (Stott and Cora 1991).

23 Intrusive Rocks There are a variety of intrusive rocks both external and internal to the RLGB. The majority of the rocks that surround the RLGB are granitoid batholiths typical of the Archean tonalite - trondhjemite - gnnodiotite ('ITG) suite. These plutons and batholithic complexes are composed of multiple intrusions varying in age and composition. The northeastern and north central part of the RLGB are bordered by the 273 l+3 Ma Little Vermilion Lake batholith (Corfu and Andrews, 1987) and the 2717+2 Ma Hammell Lake batholith (Yo& et aL 1991), respectively. The southern part of the RLGB is bordered by the 270421.5 Ma Killala-Baird batholith (Corfu and Andrews 1987). The eastern part of the RLGB is bordered by the Tmut Lake batholith. The Trout Lake batholith contains an older core of foliated tmalite flanked by younger granitic to granodioritic plutons (Stott and Co&&1991). The con of the batholith is composed of various units of foliated to locally gneissic tonalite ranging in age fnnn 2839+4/-3 Ma to 2806+12/-2 (Noble et al. 1985 and Noble 1989). The crescent shaped 2699-c 1 Ma (Noble et al. 1989) Walsh Lake pluton immediately east of the RLGB is the youngest phase of the Trout Lake batholith. The Walsh Lake pluton is a granodiorite phase that has produced a large contact metamorphic aureole affecting the rocks as far away (7 hn) as the CRLMC (Andrews et a1 1986). Intrusions internal to the RLGB include the McKenzie and Dome stocks, the Howey diaite and a number of small felsic intrusions including the Abino and Wilmar granodiorites and the Red Crest stock. Msfic and ultramalic intrusions are abundant in the eastern portion of the RLGB. The 272022 Ma (Coda and Andrews 1987) MciCFnzie stock is an elliptical composite pluton consisting of thne phases; diotite to quartz diorita, biotite granodiorite and pyroxenite (Hocwood 1940). The Mc-e and Gold Eagle Mines are hosted within hydrothemally altered portion of the McKenzie stock The 27l8+ 1Ma Dome stock is a sub-circular pluton consisting of a marginal phase of diorite to quartz diorite grading into a biotite - hornblende granodiorite ('erguson 1966). Past producers in the Dome stock include the Red Lake Gold Shore Mine and the Buffalo Mine. The Howey dioc5te is an elongate intrusive body ranging in composition fhmgabbro to quartz diorite (Athson 1993). The Howey diorite is cut by a large quartz feldspar porphyry dyke that hosted the Howey and Hasaga Mines (Horwood 1940 and Cotnford 1940). The Abino and What granodiorites are small intrusive bodies that have been dated at 2720+7/-5 Ma and 27Ol&1.5 Ma (Cocfu and Andrews 1987) and range in composition from granodiorite to trondhjernite. Both intrusions are hydrothemally altered and host small subeconomic quantities of gold mineralization (Rigg and Scherkus 1983). The 2729& 1.5 Ma (Corfb and Andrews 1987) Red Crest stock in Todd Township is a small quartz diorite intrusion that is cut by fine grained diorite dykes (Horwood 1940). Minor amounts of gold minetalization occur on the Red Summit property within the Red Cmst stock. MaFic and Ultramafic intrusions are abundant in nottheast section of the KGB. The East Bay serpentinite, predominantly serpeatinized pebdotite, is one of the largest of the intrusive ultramafic bodies in the RLGB. The East Bay serpentinite occurs discontinuously along the East Bay fault which trends northeast from the old Codrenoor- Wiians Mine along the length of East Bay (Andrews and Wallace 1983). Numerous other small felsic "QFP"dykes aad "Lunpmphyres"occur throughout the RLGB. Small felsic "QFP"dykes and "Campmphyres" in Baher Township will be discussed in the following section.

24 Geology of hherTownship The geology of Balmer Township is dominated by xnafic volcanic rocks of the Balmet and Bmce Channel Assemblages (Figure 26). The CRLMC is hosted within the Balmer Assemblage. Sedimentary mcks of the Bruce Channel Assemblage highlight the fold structures east of the CRLMC. Minor amomts of intermediate to felsic rocks of the Confederation Assemblage outcrop in the southern portion of Balmer Township. The stratigraphic subdivisions of MacGeehan and Hodgson (1981) have been revised following geochronological studies by Corfu and Wallace (1986) and Co& and Andrews (1987). The Western Volcanic Compkx and the Southern Volcanic Belt correspond to the Balmer and Coafederation Assemblages, respectively. The Central Sedimentary Belt and Eastem Volcanic CompIex correspond to the Bruce Channel Assemblage. The structural geology of Balrner Township is poorly understood due to the paucity of outcrop and detailed structural studies. Gradeci bedding and pillow tops all f= to the southwest, consistent with a monoclinal sequence (Pirie and Grant 1978; Pirie 1981 and MacGeehan and Hodgson 1981). However, immediately east of the CRLMC the map pattern suggests that there may k several tight folds. Sediments of the Bruce Channel Assemblage east of the CRLMC are highly deformed and brecciated (Plate 2-2). Intrusions in Balmer Township include numerous felsic "QFPdykes, small mafic - ultramafic intrusions and rare lamprophyres. The most conspicuous felsic intrusion is the Balmer Lake intrusion, which is also known as the Brewis porphyry (Chisholm 1951) near BaImer lake dated at 2742+3/-2 Ma (Corh and Andrews 1987). This felsic intrusion has been classified as a quartz monzonite and is composed predominantly of albite with minor microcline and quartz (Chisholm 1951). The a 1 2 3bn

Gmnodiorils to Granite \\ FolWon: (Dip lnd'ned. Vertical)

Diodte \ Redding:TopKnorvn

Tonalite to Granodkrite \ Bedding; Top Unhm

Mafic to Uhmafic Rack, Piifow Tops Known

Figure 26. Geology map of Balmer Township. Modified after Pirie and Grant (1978), MacGeehan and Hodgson (1980), Atkinson and Stone (1993) and Penczak (1996). Plate 2-2. Outcrop of tightly folded oxide facies iron formation of the Bruce Channel Assemblage. Photograph taken 800m east of the Red Lake Mine headframe looking west. "Howey Dioritem'outcrops in the southwest comer of Balmer Township and is composed of a number of phases frmn quartz dioritc to tmadhjemite with local xenolith-rich intrusive bdas(Pirie 1977). Numerous small intrr;rSions, ranging from serpentinized peridotite to coatst pined gabbro, occur locally throughout the township. A luge mafic intrusion crops out on the east si& of Balrner lake. The coarse grained gabbros are cut by the QFP dykes (Meand Grant 1978). All mcks in Balmer Township an affected by regional metamorphism.

2.5MincGeolgg The geology of the CRLMC is extranely complex. Recognizable rock types include ultramafic intrusive rocks (peridotite) and extrusive mcks (komatiites), matic volcanic flows ranging from massive-pillowed basalt to amygdaloidal basalt, felsic volcanic rocks (rhyolite), cIastic sediments ranging from argillite to Iithic wacke (turbidites), various types of chemical sediments (silicatssulphide iron formation) and several sets of felsic to matic dykes. AU of these mcb types are variably altered, metamorphosed and displaced by numerous sets of faults. Several unorthodox rock types are recognized and mapped by the mine geologists (e-g. '@Chickenfeed@@= carbonatized ultramafic rock). I.Table 2-1, each of these local rock types is matched with its inferred precursor rock type. Further references to local "Red Lake" rock types will be in quotations, and normal font will be used for their suspected precursor. The mineralogical variations of the different rock types will be discussed in more detail in Chapter 3. Figure 2-7 is a compilation of the geology from the 14th level of the Campbell Mine and the 15th level of the Red Lake Mine. Figure 2-8 is a schematic SW-NE cross-section through the Red Lake Mine. The dominant rock type and main host for ore in the Rod Lake Mine is "andesite" to "rhyolitic-andesite."Depending on the degree of alteration and precursor rock type "andesite"to "rhyolitic-andesite" spans the compositional field from komatiitic-basalt to Table 2-1. Rock types in the Campbe11 - Red Lake Mine Complex and the mine tezmiLLo1ogy. Madifid fhm Egg (1980) and Christie (1986).

- pp - - Mine Terminology Rock Type Andesite Variably altered massive to pillowed tholeiitic basalt, minor amount of variolitic and amygdaLoidal bdt,badtic-komatiite

Dickenson and Porphyritic quartz diolite Campbell Diorite

Rhyoliu Rhyolitt, may in some cases be mistaken for Acid Lava bleached basalt

Rh yolitic-Andesite Bleached basalt

Sediments Volcanclastic and epiclastic sediments, lithic wacke, (tnrbidites) oxide and splpbide iron formation

Cbickenfeed (Red Lake Mine) Highly altered mafic to dtramafic intrusive and Altered Rock (CampbelI me) extrnsive rocks

Peridotite Coarse-grained intrusive mafic to ultramafic rock

Serpentinie Serpentinized ultrarnafEc intrusive mcks n-r .- SCHEMATIC CROSS-SECTION OF THE RED LAKE MINE SW

Figure 2-8. Schematic vertical SW-NE cross-section of the Red Lake Mine through the shafr tholeiitic basalt. The majority of the basalts have been classified as iron-rich th01eiites (Pirie 198 1: MacGeehan and Hodgson L981). The degree of alteration can be roughly judged by the intensity of bleaching of the mcks, which approximately cotresponds to leaching of the allalis. The most intensely bleached mch are composed hostentirely of qpaaz and andalusite (see Chapter 3). This type of alteration has been termed early alumhops alteration by Penczak (1996). The least altered rnafic volcanics are typically very fiegrained, dark pen to black massive flows. Strongly bleached mafic volcanics may easily be mistaken for rhyolite. lhdividual bdticflows can often be distinguished and mapped on a local scale from massive aphanitic flows using textural and mineralogical criteria such as pillows, amygdoles, varioles and garnets. The 'pickenson diorite," which is equivalent to the "Campbell diorite,' may be a coarse grained equivalent to the basaltic flows (Rogers 1992), a clastic sedimentary rock with a bimodal source (Kosmirski and Crocket 1980; Mathieson 1982) or a true felsic intrusive rock (e-g. quattz diorite porphyry, see below). A rich variety of ultrame rocks occur in the CRLMC. Mine terms range fmm "Chickenfeed"at the Red Lake Mine to "Altered cock" at the Campbell Mine. The origin of this rock type is very dubious because primary textures are rarely preserved due to extensive and highly variably pre-metamorphic alteration. However, relic spinifex, typical of komatiites and relic serpenthized olivine phenocrysts, typical of peridotites have been observed (Penczak 19%). Relic spinifex was not observed in the "Chickenfeed"at the Dickcnson, but was observed by Fend(1996) in "altered rock at the Campbell Mine. A dioritic unit, referred to as the "Campbell and Dickenson diorite by mine geologists and called a "quartz-gabbro"by Corfa and Andrews (1987), with distinctive blue quartz "eyes" is often associated with "Chickenfad" at the Red Lake Mine. This association was used by Rogers (1992) to suggest that the "Chickenfdmay be an intrusive unit Zircons From the "quartz-gabbro"yielded an age of 28702 15 Ma (Cocfu and Andxews 1987) which clearly post-dates the volcanic rocks. Although, some of the quartz "eyes" an polycrystalline agpga, bipynmidal kartzphenocrysts are still discetnib1e. This provides clear evidence that the "Campbell and Dickenson dioritesnare intrusive, but sheds no light on whether or not the "Chickenfeed is intrusive or extrusive. Textural evidence points to the fact that the dtramafic rocks in the CRLMC are partly intrusive and extrusive. The ultrmafic rock types are very incompetent due to a high percentage of carbonate and talc and hence, highly deformed . The competency contrast between the dtrsirnafic rocks and the more competent mafic volcanic rocks has been extremely important in the localization of ore (Rogers 1992 and Penczak 1996). In contrast to the Campbell Mine, very little ore occurs in the "Chickenfeed" at the Red MeMine. Rogers (1992) specdates that this may be due to the original strike of the unit or varying metamorphic or geochemical conditions that may affected the competency of the unit It is highly UnWEely that metamorphic conditions varied sufficiently between the two mines to have resulted in differences in competence. It seems more likely that the "altered rock" at the Campbell Mine was pervasively altered as a result of its more dilatant relation to the local strike-slip fault system (Penczak 1996)- Minor rhyolite occw in the CRLMC. Most of the felsic volcanic rocks occur in the eastern end of the CRLMC within the Red Lake Mine* Rhyolite is commonly called "Acid Lava" by mine geologists. Mathieson (1982) assumed that the "Acid Lava" may have a sedimentary origin, but whole rock data show that it has a high Ti% content typical of felsic volcanic rocks. Rhyolite is typically a massive, fine-grained light grey rock with local volcanic breccias and tuffaceous horizons. Mineralization hosted within felsic volcanic rocks is restricted to the "H" zone at the Red Lake Mine, within a few meters of the contact with ultmnafic mcks. The "S"zone of the Campbell Mine is hosted by mafic volcanic rocks within a few meters of and mbpareUe1 to felsic volcanic rocks* Other less ab~dantrock types interbedded with mafic volcanic rocks in the CRLMC inch& clestic sedimentary rocks and banded imn formation in sulphide sad oxide facies. Minot mopats ofclastic sediments occur in the eastern portion of the CRLMC within the boundary of the Red Lake Mine northwest of a large serpentinite intrusion (Figure 2-7). Clastic sediments observed undergmmd are predominantly dark grey to black, hegrained, massive to crudely bedded litbic wackes. Interbedded mrbidites and iron formation on sarface immediately east of the Red Lake Mine shaft are similar and may be related. No alteration or mineralization is associated with clastic sedimentary rocks. Banded iron formation is associated with mineralization only where it is cut by other orebearing structures (Rogers 1992). There are numerous dykes within the CRLMC. Both igneous and sedimentary rocks as well as ore zones are intmded by quartz feldspar pcphyries (QFP) and "lamprophyres"(PIate 2-3). The QFP dykes are generally dull grey, less than one meter thick and subvertical. Chilled margins were observed underground. "Lampmphyres"are typically fine-pined, black and less than one meter thick with variable orientations. Corfa and Andrews (1987) dated a post-oce QFP dyke on the 16th level of the Red Lake Mine at 2714k4 Ma. This provides a minimum age for mineralization in the ClUMC. Both the "lamprophyres"and QFP dykes are cut by numerous subvertical faults tenned "black-line"faults by mine geologists. ''Black-line*8faults can have either right and left- handed off-sets up to about 800 meters (Rogers 1992).

26 Structural Geology, Alteration and Minerdization A detailed study of the stmchual geology, alteration and mineralization of the CRLMC is beyond the scope of this study. Consequently, only the principal aspects will be reported. For more information on studies that focused on structural aspects and their Plate 2-3. Flat-lying "lampmphyre" dyke cmss-cutthg ore at the 15-1573HW of the South "C" ore wne. The scale card rests on the contact between the sulphide-banded ore to the top and the bgtained black "lamprophyn"dyke to the bottom of the photograph. Note the contact is horizontal and very sharp with a thin (4.5cm) calcite vein madting the upper contact. Photograph taken looking southeast. relationships to gold mineralization of the CRLMC the reader is referred to Rigg (1980) and Rogers (1992). For a more thorough treatment of aspects reganling mineralization with insight into the structural controls the reader is refemd to PenRPk (1996). The mean strike ofthe dominant schistosity in the mine is 126O and varies between 113O and 142O and the dips range fmm 42O to 72O. Although, Rigg (1980) defined two dominant schistosities in the mine, this obsemation was not confirmed by Mathieson (1982). Based on the apparent displacement of imn formation and the

ultrama& units Mathieson (1982) suggested that the CRLMC was ttansected by a strike- slip fault system 2-7). The northern (Campbell Fault Zone) and the southen (Dickenson Fault Zone) fault system ace dominated by sinistral and dextral movement, respectively. The complexity of alteration is best expressed by the numerous interpretations of previous workers (Pirie 1982, Mathieson 1982, Mathieson and Hodgson 1984, Lavigne and Crocket 1982, Andrews et aL 1986). In tenns of gains and losses, alteration in the CRLMC, has been interpreted by Pirie (1982) to have resulted largely in the addition of Si%, A.1203,K20, Sb and As with the subtraction ofNa20, CaO, MgO and total Fe. Mathieson (1982) and Mathieson and Hodgson (1984) interpreted the alteration in the ESC ace zone to have resulted in thc addition of FeO, Fez03 and MnO with the subtraction of CaO, MgO, Na20, and K20 relative to unaltered pmtoliths. Contrary to this conclusion, K20 is quite clearly strongly enriched in the basaltic rocks relative to unaltered protoliths (see pg. 8 1 Table 4-1 of Mathieson 1982). Lavigne and Crocket (1982) have interpted the alteration in the ESC ore zone to have resulted in addition of K20, total Fe, S, Au, As and W, and depletion of Ca and Mg. Andmws et al. (1986) have described two main types of alteration based on the presence of either calcite or ferroan dolomite. The calcite alteration in the greenschist domuin is described in terms of the addition of C0.L and Hz0 with sporadic, minor depletion of total FeQ MgO and Na20. The ferroan dolomite alteration is expressed by variable, but significant additions of SiOy, K20 and S with large depletion of -0, MgO and Na20. Large areas within the ferrour dolomite domains are sili&ed resulting in elevated values of Si% and A1203 This is interpreted to have resulted largely from a residual enrichment due to the removal of COO, MgO and Na20. Andrews et aL (1986) describe alteration within ~~~hibofiiedomuins as largely the some as in the penschist domains apart from the absence of C*. This conclusion does not apprto hove meut because ankerite is present as an abundant alteration phase throughout the lower levels of the Red Lake Mine. Pennak (1996) pointed out that the present mineralogy and geochemistry of altered rocks are the result of a complex superposition of alteration assemblages. The irregular distribution of the geochemical patterns and some of the mineralogical patterns ace the result of this complex superposition, which has partially preserved early alteration minerals (e-g. biotite and chlorite) in some areas while totally destroying them in others. This fact along with the variable rock types points out that using bulk-rock geochemical analysis as a guide to ore most be interpreted with caution. Mineralogical variations typically reflect the earlier alteration patterns. Mathieson (1982) and Mathieson and Hodgson (1984) described minedogid variations around the ESC-ore zone. They =port three fees of alteration mineral assemblages in tern of ddgintensity from gomet fda to biotite-chlorite fbes to hornblende focics and finally unaltered tholeiitic basalt. It is important to note that they did not identify any unaltered tholeiitic basalts in their study. According to Mathieson (1982) and Mathieson and Hodgson (1984), the garnetfacies represents the most altered basaltic rocks and occurs proximal to primary features such as pillow selvages, pillow rims and flow top bfeCCiSiS. The mineralogy within the gmwtfm'es consists of variable amounts of Grt + Bt + Chl + Cld + St + And. The next alteration fPcies outward from the game! facies is the Biotite-Chlorite f&es. The mineralogy of this facies is characterized by the disappearance of garnet and the absence of hornblende with abundant Fe-chlorite and biotite. This alteration facies is also distinguished by the decrease in modal abundance of the aluminous minerals. It is important to note that they describe Fechlorite as disappearing distally before biotite. This is in contrast to mineralogical zoning described by Pen& (1996) and this stady (Chapter 3). They also note that gamet md hornblende never occar together in the study. However, garnet and hornblende have ban identified dvoughout the mine. The next alteration facies is the Hornbendtf&cs. It is characterized by the appearance of hmbkDdc and the gradual disappearance of chlorite followed by biotite. No aluminosilicate minerals occur in this alteration facies. Pend (1996) described the mineralogical variations of alteration in the Campbell Mine. He describes the highly altered rocks of the mineralized zones as being affected by biotite alteration which is overprinted by sericitic or chloritic alteration. He also states that chloritic alteration usually flanlcs zones of pervasive biotite alteration and even has remnants of the earlier biotite preserved within the chlorite. Alwninous alteration, typified by Grt+Cld+Mrg+Crd+And at the Campbell Mine, usually occurs outboard of the highly altered zones in the bdt Inside of the aluminous alteration, amphiboles (Ath+Cwn) appear in siliceous zones. This will be discussed fiuther in Chapter 3. Recently, Pen& (1996) postulated that the early strike-slip fault system was the locus of intense hydrothemal alteration and subsequent mineralization in a high level epithemal environment. Evidence supporting this conclusion is the presence of huge (up to 18m wide) crnstiform banded veins, cockade breccias, bladed carbonate, crack- seal textures, vein breccias, multipIe phases of hydmthermai breocias, zoned aluminous mineral assemblages and anomalous Au-Ag-As-Sb-Hg-Zn-Ksimilar to recent low- sulphidation epithemal deposits (Sillitoe 1993). Mineralization, however, is later than aluminous (argillic - advanced argillic alteration) and related to silicification, sulphidation and re-brecciation of the pre-existing vein systems with minor quartz- carbonate veining. 2.7 Solmaary of Geological Events

A s~rrrmaryof the geological events in the Campbell-Red Lake Mine Complex (CRLMC)is presented in Table 2-2. Volcanism in the CRLMC is constrained to 2989 t3 M. (Cob and Andrews 1987) fmm a rhyolite on the 20th level of the Campbell Mine. Following volcanism, the sequence was subjecteci to a period of foIding and thrusting. Subsequent intrusion of the Dome and MacKeIlZie stocks at 2718 tl Ma (Corfb and Wallace 1986) and 2720 t2 Ma (Corfa and Andrews 1987), respectively, cut these early fold patterns (rrorwood 1940). The belt must have then been subjected to another period of uplift and possible subaetial exposure dtuing which time the strike-slip fault system and subsequent alteration and epithermal style mineralization occurred in the CRLMC. Following the alteration and mineralization event the mine sequence was intruded by felsic (QFP) and metic ("lmp~ophyre*')dykes. tampmphyre dykes have not been dated but have been observed aoss-cutting a QFP dyke on surface. This episode was succeeded by the intrusion of the Walsh Lake Pluton, contact metamorphism and finally regional metamorphism. The post-mineral QFP and lampmphyre dykes and the marginal phase of the Trout Lake Batholith (Walsh Lake Pluton) are foliated. The foliation and metamorphic recrystallization have overprinted both hydrothermal alteration and subsequent gold mineralization. The age of mineralization is constrained by QFP dykes cross-cutting ore dated at 2714 14 Ma (Corfo and Andrews 1987). The emplacement of the Walsh Lake pluton (the marginal phase of the Trout Lake batholith) occurred at 2699 tl Ma (Noble et al. 1989). Bloddng dates for hornblende from the Walsh Lake pluton indicate a thermal resetting at 2650 Ma (Wright and Yo& 1990). Regional metamorphism and penetrative deformation is constrained by At-Ar blocking dates of 2647 219 Ma and 2608 t4 Ma (Yo& et aL 1991) hmbiotite and moscovite, respectively. These ages appear rather problematic. The closing temperatures for hornblende, muscovite and biotite are about

Table 2-2. Sequence of events in the vicinity of the Cmpbell-Red Lake Mine Complex. ModitEd from PenaJt(1996). SO0 do%, 350t5OoC and 30W5o0C, respectively (Berger and Yodr 1981, Reynolds 1992). The age for muscovite appears to be oat of order for a noma1 cooling path. This may be due to the fme gnin size of mllscovite used fadating (J. Haaes pen. comm. 1997) However, this still broadly reflects the age of the Kenoran thermo-tectonic event across rhc whole Superior Province (Stockwe11 1%1). 3. Metamorphic Petrology

3.1 Introduction More than 200 thin sections were examined in order to document the nature and distribotion of low-variance mined assemblages witbin the Campbell-Red Lake Mine Complex (CRLMC). Extremely fine-grain size (60pm) makes hand-specimen identification of mine& very difficult. The only aluminous mined that is readily visible in hand specimen is garnet Therefore, sample collecting focused on basaltic rocks with visible garnets and where previous workers (Mathieson 1982) had noted low- variance (Le. many different minerals) duminons assemblages. Most of the rocks are inferred to have suffered extensive pn-metamorphic hydrothermal alteration such that the resultant bulk compositions of the basaltic rocks now plots in the bullr composition range of pelitic rocks (Figure 3-1). Subsequent metamorphism of the highly altered

basaltic rocks has created a rich variety of alaminous mineral assemblages sirnilar to that observed in metapelites. Many of the metamorphic mineral assemblages in the highly altered basaltic rocks have low-variance mined assemblages, and this makes it possible to tightly constrain the conditions of metamorphism. Samples for petrographic analysis were collected from surface outcrops, surface and underground dtill-holes, and from underground along drifts and c~oss-cutsin order to get the greatest spatial variation possible. In the following subsections, the nature and distribution of the various mineral assemblages and chemistry of rninerafs analysed in the rocks of ?heRed Lake Mine will be discussed. For a complete discussion of carbonate minerals refer to Rigg (1980). MacGeehan and Hodgson (1982) and Penczak (1996). Refer to section 3.16 (Figures 3- 4,3-5 and 3-6) for the map locations of samples mentioned in the text. Refer to Appendix A for a complete list of samples and an explanation of the nomenclature used Figore 3-1. ACF diagram of rocks frwn the East South "C" ore zone illustrating the bulk compositions of: 1) basah and mdesites and 2) shales and pywackes (Best 1982). Hydrothermal alteration is infed to have changed the bulk composition of basalts and andesites such that all ten of them now plot in the bulk composition range of shales and greywackes. From Mathieson (1982). A=&O,, -80, F=FeO + MgO. for labeling. Refer to Appendix B for complete tables of electron microprobe analyses and structural formulae.

3.2 Mineral Assemblages Samples were collected fran most mdrs types in the Red Lake Mine inciuding sedimentary rocks, dtramafic rocks, extrusive feEc rocks ("Rhyolite"), intrusive felsic rocks ("CampbelVDickeason Diorite"), various dyke cocks including QWs, 'lmpmphyres," and amphibolite dykes, and basaltic rocks ("Andesite"). Only the maximum-phase assemblages will be documented below because they impose the most stringent restrictions on metamorphic pressares and temperatures. Refer to the list of minerals and their abbreviations at the beginning of the thesis. 3.2.1 Sediments Metasediments from surface outcrops east of the Red Lake Mine headfkame are tightly folded and composed of interbedded turbidites, lithic wackes, sedimentary breccias and banded iron formation. Representative mineral assemblages in sedimentary rocks are listed in Table 3-1. Samples of turbiditic sediments (Sample S-1,800m east of the Red Lake Mine h-e) and Ethic wacke (9518-1) from surface contain two separate maximum-phase assemblages, respectively: (l)And+Cld+%t+Chl+Pl+~ (2)Grt+And+Ms+Bt+Chl+Pl+Qrz These assemblages are representative of amphibolite facies. Underground, sediments were collected fiom the 16th level (16-5555A/B). Sample 16-555!5B is pelitic and contains two texhualLy distinct generations of Cld: early syn-tectonic and late syn- to post-tectonic (Plate 3-1AIB). The maximum-phase assemblage in sediments from the 16th level is:

(3) Grt+And +Cld+Ms +Bt +Chl+Pl +Qtz Plate 3-lA. Two distinct textural genetations of cfrloritoid (ad) in sediments. The arrow points to an early syn-tectonic, subequaut, anhedd porphpbIast of Cld with sygmoidal inc1usion trails. The late syn- to post-tectonic, subbedrPL Cld porphytoblasts en tabular and display welldeveloped hop%lass strac~with poody developed sygmoidal inclusion rtails. Sygrnoidal inclusion tRils in both cases err defined by inclusions of ilmenite and quartz Shear sense is dextral and is mpdGed in the upper right hand corner of the photomictograph. The matrix consists of garnet, addosite, muscovite, quartz, pIagiocIase, biotite, chlorite, ankerite and ilrnenite. Plane polarized light Sample 16-555SB. 16fh level.

Plate 3-1B. Same sample as above showing the two distinct textural generations of Cld. Note that both generations have sygmoidal inclusion trails with a dextral shear sense. Garnet (Grt) porphymbhts (upper right hand comer) also commonly display sygmoidd inclusion trails with a dextral shear sense. Plane polarized light. Sample 16-555B. 16a level.

Assemblages (1) aud (2) am subassemblages of (3). It is important to note that no stamlite was obsemd in any of the meuscdiments. This is most lilcely doe to intrinsic differences in bulk compositions (Le. CaO or MnO in the system K20 - FeO - MgO - A1203 - Si@ - H20). Sediments from the 2& level (Samples 2439 and 2441). termed "Chemical sediments" by mine geologists, have high-variance assemblages with no aluminosilicate minerals and are therrfore not useful indicators of metamorphic grade. Mathieson (1982) reported sillinrank in sediments fhm the 23d Level (Sample 118- 3 1). However, on faaher examhation of this sample, it becomes apparent that sillimanite was mistaken for masgadta This was confirmed using optical properties. Margarite is biaxial negative and has lower birefringence than sillimanite. Margarite in this sampk displays a well developed crenulation. The mineralogical assemblage consists of: (4)And+Mrg+Ms+Chl+Q@+Pl+Rt Metasediments were not observed below the 24th level of the Red Lake Mine. It is apparent fkom the maximum-phase assemblages that metasediments obsecved in the CRLMC represent amphibolite facie assemblages.

3.2.2 Ultrarnanc Rocks Ultrarnafic rocks in the CRLMC are refed to as "Chickenfeed"at the Red Lake Mine and "Altered Rock" at the Campbell Mine. Sample collecting did not focus on the ultramaiic rocks and therefore only a brief description follows. Representative mineral assemblages of ulttarnafic rocks are given in Table 3-2. The majority of ulttamafk rocks in the mine are highly veined, carboaatized and locally silicified. However, relic olivine phenocysts and spinifex have been observed (Christie 1986 and Pend1996). Maximum mineral assemblages preserved in ultrarnafic rocks in the Red LaLe Mine are: (1) Ath+TIc+Chl+CrbtQa+T~ Table 3-1. Mined assemblages in metasediments.

L ------Sample # Grt And St Cld Mrg Ms Bt Chl PI Qe Crb Ap Rt Tur Op

S-1 X X XXXX X

9518-1 X X Serxxxx X

LdSSSSA x XXFeXX X X

16-55558 X X XXXXXX X

118-3 1 X X X XXX X X

2439 X X XXX X X

2441 X X Mg XXX X X

Table 3-2. Mineral assemblages in altered ultramafic rocks.

-

Sample # Ath Cum Act Tm Tlc Hbl Bt Chl PI Qtz Crb Ap Tur Op

9512-1 X X Mg X X X

95 12-2 X X Mg X X X

1557 ? X Mg X X

1597 X Mg X X

38L-O1-7 X X xxxxxx

38fr01-8 X XXX X Note: Miacral abbreviations after Kretz (1983). Op = opaqucs, X = present, set = sericite, Y= scpamtc z~ssc~llbiage,x = present in miwr amounts, Fe = icon-rich. Mg = magnesium-rich. Optically, the carbonate phase lacks twinning and has higher relief than calcite or dolomite and is therefoe probably magnesite. Altaed ultmnafic mcks at the Campbell Mine may be rich in A1 and contain abundant cotdierite as well as sericite + fpcbsite + quartz + biotite + leucoxew + rutile (Penczak 1996). AlOminous alteration of dtramafic rocks has not been observed in the Red Lake Mine.

3.2.3 Felsic Extmdve Rocks In the Red Lake Mine, the term "Acid Lava" is wed to describe pale greyhpff schistose mcks that may have originally been rhyolite. The identification of rhyolite in the CRLMC is difficult because rhyolite looks very similar to "bleached" metabasalt "Bleached"basaltic rocks are dull steely-grey and composed almost entirely of mdalusite and quartz; in hand specimen they an easily mistaken for rhyolite. Samples indicative of "Acid Lava" generally contain abundant andalusite, margarite, cordierite and muscovite compared to basaltic rocks. Andalusite commonly overgrows the foliation defined by tabular ilmenites and phyllosilicates aml is only slightly rotated (Plate 3-2). Locally, plycrystalline quartz domains with the external form characteristic of igneous kuartz phenqsts are preserved. Representative mineral assemblages of felsic volcanic rocks ("Rhyolite") are given in Table 3-3. Altered rhyolite collected fnnn the 15fh level of the Red Lake Mine (15-017A) contains: (l)And+Mrg+Ms+Qa This differs From samples collected fnun the 34th level which contain the assemblage (Plate 3-3): (2)And+St+C~i+hftg+Bt+Chl+Pl+Qe In the Campbell Mine Pend(1996) noted other aluminous minerals in "Rhyolite" including garnet and chloritoid. 3.2.4 F&k Intrusive Rocks The "CpmpbeWDickenson dioritc" is a distinctive rock unit in the CRLMC which commonly contains blue qoPrct "eyes" (Plate 3-4). Although some of the quartz "eyes" consist of polycrystaIIine aggregates of quartz, bipyramidal morphology typical of euhedd igneous &quartz is lodyptesecved (Plate 3-5). Other relict igneous textures are skeletal ilmenite and magnetite as well as tabah aggregates of biotite possibly pseudomorphing igneous phenocrysts (Le. hornblende). Mousinterpretations of the "CampbelVDickensondiorite" are contradictory. It has been interpreted to be a true quartz diorite (Moddle 1962), volcaniclastic sedimentary rock (lbmhki and Crocket 1980, Kusmirski 1981 and Matbieson 1982), or a coarse- grained equivalent of the basaltic rocks (Rogers 1992). However, U-Pb zircon dates by Corfu and Andrews (1987) yield an age of 2870 a 15 Ma which is approximatdy 120 Ma younger than the volcanic mcks. Chisholm (1951) noted that Campbell diorite cuts volcanic stratigraphy in an irregular manner. The "CarnpbeU/DickensondioriteS* is most likely an altered porphydtic quartz diorite. The "CampbelllDickensondioritett has been overprinted by all phases of alteration including biotite and chlorite aheration, carbonatization, silicification, aluminous alteration and in some instances mineralization (Penczak 1996). This complex series of alteration followed by metamorphism results in a rich mineral assemblage preserved in the 'CampbelVDickenson diodte" flable 3-4). Relatively unaltered samples (e-g. 9512-3) collected from surface drill holes contain the assemblage: Bt+Chl+Pl+Qtz+Ank Apatite and tourmaline are relatively abundant accessory phases (Plate 33). This assemblage is in stark contrast to highly altered samples collected within the Red We Mine which contain the maximum-phase assemblage:

Grt+And+St+Cld+Bt+Chl+PL+Qtz+Ank - - Sm# *And St QdCrdAthBMWg Ms Bt Chi PI Qb Crb Ap'ILr Op 15417A1 X X X X ftm 24-88-4 ? X XXMgX XXXXX 2416 X xXx X X XXX 34L-235-1 X X X XXXX X XXX X 34L-2364 X X X X X XMgAn82X x Ilrn 38LOl-6 X X MK X X x X

Table 34. Mineral assemblages in "Dioritcw.

L

SmplcW Grt And St Cld Crd AthEblMcg Mi Bt Chl Pl @ Crb Ap Tur Op 95 12-3 XX X XXXXX 95 16-2 x X MgX XXX X 9517-1 ? X X X XX X 17-2347 X X? X- Mg X XXXXX W23 XXXX X Fe An70 X Ank llin 2415 XXX XXPc X XX X Plate 3-2 Latetectonic andalusite (And) paphymblast in "Acid Lave" The large euhedral And paphpblast grew over the foliation in the rock defined the alignment of muscovite, margadte, quartz and ilmenite and was subsequently rotated sinistrally about 20'. Shccrr sense is indicated in the upper right hand cowr of the photomictograph. Plane polan'7Pd light, Sample 15-01fB. 15fh leveL

Plate 3-3. Large anhedral poikiloblast of cotdierite (Crd) in a felsic volcanic? rock. The arrow points to a small euhadral zincian stamlite (St) inclusion in the cordierite porphymbIast. Note the golden yellow bbfeingence of the margarite @kg) in the lower left hand corner. The matrix is composed of margarite, muscovite, biotite, chlorite, quartz, plagioclase, andalusite, stawolite, apatite and ilmenite. Crossed polarized light. Sample 34L236-1.Underground DDH 34L-236,55.13 m (181 ft). 34th level

Plate 34"Campbelyoickenson dioritem with coaspicoous blw q- "eyes." Also note the fine skeletal ilmenite aggregates. Hud specimen. Sample 9512-3. From spcface DDH GC-95-12, 353 m (1150 10).

Plate 3-5 Photomicrograph of the same specimen as above with relic igneous kuattz phenocrysts with straight extinction preserved in the "CampbelVDickenson Diorite." Matrix is composed of chlorite (Chl), biotite, quartz (Qa), plagioclase, apatite, ankerite and tourmaline (TIM).Cross poladzed light. Sample 9512-3. Fmm srrrfiice DDH GC-95-12, 353 m (1150 ft).

The above assemblage is identical to that of many of the highly altered basaltic rocks (see 3.2.6).

3.2.5 Dykes There ace numerous sets of dykes in the CRLMC incIuding quata-feldspar porphyries (QFP), "lampmphyres" and arnphibolite dykes. Evidence in Chapter 2 clearly shows that aIl dyke rocks crossat the regional foliaton and that ldythe dykes cross- cut ore (Plate 2-3). AU of the dykes display a weak foliation and most have sheared and veined contacts. Mineral assemblages in the mphibolites consists of approximately 60% hornblende and 30% plagialase with lesser amounts of chlorite, biotite and ilmenite. Sample 1627 was collected from the 16th level of the Red Lake Mine from a rock type known as "Peridotitd' to the mine geologists, However, the mineralogy is not consistent with that of a metamorphosed peridotite. It is similar to an maltered but metamorphosed rnafic volcanic rock (i.e. amphibolite). Other amphibolites in the mine appear to be completely unaltered, but metamorphosed mafic (diabase) dykes consisting of subequal amounts of randomly oriented hornblende and plagioclase with minor (40%) quartz and biotite (e-goSample 118-20 brnMathieson 1982). This implies that the amphibolite dykes and the "Peridotite" were introded prior to metamorphism, but after hydrothermal alteration. Although, "lampmphyres"were observed ctoss-cutting QFP dykes, amphibolite dykes were not observed cross-cutting other dykes. Because the amphibolite dykes appear to be unaltered but metamorphosed equivalents of mafic (diabase) dykes, it is assumed that they are younger than the QFP and "lamprophyre" dykes. Mineral assemblages in the dyke rocks are summadzed in Table 3-5. The main alteration minerals in the QFP and "lamprophyre" dykes are sericite, biotite and Table 3-5. Mineral assemblages in dyke rods.

Sample # Grt Hbl Ms Bt Chl PL Qtz Crb Ap Tur Op Rock Type 1627 X XXXXX x X Amphibolite 157-28 X set X XXXXx x Qm 28-886-A1 ser X X X x ~P~OP~P 28-88642 ser X X X x -W?wh~re 28-886-2B ser X XXXX x Qm 30-886-A ser X XXXXx x Qm 30-886-B ser X XXXXx x Qm 30-867 XXXXX X -Lamprophyre Notc: Mineral abbreviations rffct Ectz (1983). Op = oppqucs, X = pesent, sa = &cite, Y= separate rssanblagt, x = present in minot amounts, Fe = hricb, Mg = mpesium-rich. Plate 3-6. Garnet (Grt) porphyroblast in gnartz-feldspar porphyry (QFP)dyke. Note the large phenocrysts of clear qartz (Qct) with straight extinction and the "cloudy" plagioclase (PI) phenocrysts. Matrix is composed of biotite, chlorite, plagioclase, sencite, quartz, apatite, zircon and ankerite. Cross polarized light. Sample 157-28. Mathieson (1982) ~~Uectioa23d IeveL carbonate. Oniy minor chlorite was 0bSe~ed.Garnet was obscrved in one QFP dyke fnnn the 23rd level of the Red Lake Mine (Plate 3-6).

3.2.6 Basaltic Rocks Metabasah is by far the most voluminous and diverse mck type in the CRLMC. This diversity is mdested in the wide variety of low variance mineral assemblages observed in the CRLMC (Table 36). Altered metabasalt commonly contain a variety of duminous minerals (i.e~cbloritoidstaurolite, andalusite, e-tc*).The maximum-phase assemblage includes: Oit+And+Stf Cld+Bt+Chl+PL+Qa+Crb+Tur+ApiClun

Cummingtonite commonly occars in this assemblage as inclusions in garnets and in distinct bands that cmss-cut the fabric of the rock. Opaque oxides, identified with reflected light microscopy and confinned with electron microprobe analyses, commonly consist of varying amounts of ilmenite and magnetite- There is also a wide variety of sulphides inciuding pyrite, pyrrhotite, amempyrite, chalcopyrite, sphalerite, stibnite and rare rnolybdenite and galena. Other minerals observed in thin section and confirmed with the electron microptobe include scheelite, scapolite (meionite) and dumortierite. Other aluminous assemblages in altered basaltic rocks are simply subassemblages of the above maximum-phase assemblage xninus gamet, staurolite, chloritoid andlor andalusite. Garnets are the most obvious indicator of alpminous alteration, but other aluminous minerals (e-g. andalusite, staurolite, chloritoid) may be present in rocks that lack garnet. Basaltic rocks with co8tsegrained garnets and hornblende were observed in drill holes near the Red Lalre Mine headframe (Sample 9521-1). Garnets are commonly abundant in pillow selvages of basaltic rocks which contain the assemblage: Grt+Bt+Chl+Cum+Mt+Ilm

Other mineral assemblages that contain garnet without other alurninoas minerals commonly contain hornblende. This characteristic assemblage consists of:

Gn+Hbl+Cum+N+Bt+Pl+~+Anlc+To+Scp This mineral assemblage typically occm distal fmn the more alnminous 8ssembIages with respect to the mineralization. The diverse mineral assemblages result from a complex supelimposed types of pre-metamorphic hydrothermal alteration as well as varying metamorphic conditions. The most highly altered rocks occur in flow tops, pillow interstices, fa& and lithological contacts (Mathieson 1982, MacGeebn and Hodgson 1982 and Pend

1996), and it inferred that pre-metamorphic hydmthermd alteration was largely controlled by primary permeability and fhctures (MacGeehan and Hodgson 1982). Aluminous alteration is also more or less symmetrically developed around mineralized veins (ie. the "Main Zone"). Mineral assemblages in basaltic rocks enveloping the "Main Zone" on the 34th level of the Red Lake Mine will be discussed in section 3.15. It is clear that basaltic rocks have adopted the bulk cornpition of high41 pelitic rocks due to pre-metamorphic hydrothermal alteration. This is evident ftom the dominous mineral assemblages in basaltic rocks including garnet, aadalusite, chloritoid, stamlite, cordierite, margarite and durnortierite. Primary igneous textures, such as varioles and pillow selvages are still discernible in highly altered basaltic rocks. Metamorphic grade has also innuend the presence of certain minerals including chloritoid and stamhe (see section 3-16).

3.3 Garnet Garnet is the only aluminous mineral mdily identifiable in hand-specimen. It occurs throughout the CRLMC and becomes more abundant with increasing depth (Rogers 1992, Pen& 1996). Garnets commonly occur as disseminated crystals and rarely in veins with biotite and quartz. They range in size from SO pm up to lcm and are typically 2-3mm in diameter. Well developed poilriloblastic textures are common. Ihclusions found in garnet are typically quartz, fibrous cummingtonite, anketite and various opaque miaeraIs including magnetite, ilmeaite, acseaopyrite, pyrite and pynhotite. In one thin section from the ESC-ore wne (Sample AP-24), gold dong with arsenopyriu occurs as distinct inclusions within garact and not along ftacttms. It also interesting to note that rocks with garnets containing abundant carbonate inclusions generally have very little carbonate in the matrix. Other transparent minerals in garnets include chlorite, chloritoid and apatite. Inclusions tend to be most abundant in the cores and decrease abruptly towards the rims (Plate 3-7). hc1usion trails in syn-kinematic garnets are commonly sygmoidaL However, post-kinematic garnets that grow over the internal schistosity of the mck were also observed (Plate 3-8). The rims of garnets tend to be inclusion-fzlee and commonly consist of a mosaic offhograined euhedral subcrystals. Chemically, the garnets within the CRLMC are predominantly almandine with a significant spessartine component flable 3-7). The grossular and pympe components range between 0.040-0.143 and 0.027-0.108, respectively. The grossular component is somewhat higher than typical pelitic rocks which usually have less than 0.050 (Deer et id. 1982). Garnets display normal growth zoning prof51es typical of prograde reactions (Hollister 1966, Tracy 1982). The most obvious zoning relationship is a continuous decrease in Mn and a concomitant increase in Fe towards the rims. This relationship was also observed by Mathieson (1982). Christie (1984) and Pend(1996). The Mg/Fe ratios also decrease regularly towards the rims of the garnets, although the garnets contain a very low pyrope component. Most conspicuous is the high spessiutine component within the highly altered rocks (up to Xsps 0.297). Garnet in a basaltic rock not associated with mineralization or aluminous alteration near the Fted Lake Mine headframe (Sample 9521-1) has a distinctly lower overall spessartine component (Xsps 0.156) and higher grossular component (Xp0.143). Plate 3-7. Euhedral garnet pacphyroblast with abundant inclusions of anrifemus arsenopyrite as well as pyrite, magnetite and pyrrhotite. Note that the opaque minerals are concentrated in the core as the gamet initially grew rapidly. As growth pmweded and slowed the incIusions were expeIled from the gamet resuIeing in a clear euhedral rim. This specimen demonstrates that the ore-bearing amnopyrite was present prim to garnet growth and hence, metamorphism. Plane polarized light Sample 2471. Mathieson (1982) collection. 24fb level.

Plate 3-8. Latetectonic garnet (Grt) porphyroblast in altered basalt overgrowing the foliation defined by biotite (Bt), quartz and anddusite. Biotite is slightly deflected around the top of the labeled garnet. However, the gamet completely overgrows the foliation near the bottom of the labeled gamet. Matrix is composed almost entirely of biotite and plagioclase (An90) with lesser amounts of staurolite, chlorite, tourmaline, scheelite and ankerite. The clear equant crystals in the matrix are plagioclese. Opaque minerals are ihenite, yrite and magnetite- Plane polarized light Sample 15-017A. 15 8level.

Table analyses of garnets from the Red Lake Miat.

Garnet 9521-1 15-017A 2413 24-88-1 28-886-2D Core Rim Core Rim Core Rim Core Rim Cote Rim Sin 37.08 37.10 37.72 37.63 36.86 36.84 37.83 37.64 37.49 37.41 A1203 Ti02 Fa03 FeO MgO MnO cao Na20 K20 Cr203

Structural forrnnlae:

End-Member Compositions

Alm 0.651 0.679 0.539 0.604 0.724 0.758 0.630 0.796 0.567 0.601 pr~ 0.027 0.028 0.090 0.089 0.063 0.055 0.068 0.064 0.108 0.106 SPS 0.161 0.156 0297 0.246 0.130 0.112 0.217 0.085 0.257 0.233 Grs 0.143 0.125 0.066 0.055 0.072 0.063 0.057 0.040 0.061 0.056 Adr 0.016 0.008 0.003 0.000 0.009 0.006 0.019 0.009 0.001 0.003 Uva 0.003 0.003 0.004 0.006 0.003 0.006 0.008 0.007 0.006 0.002 Note: of analysts; Ah=ahandinc, Prp=pyropc, Sps=spessartint, Grsgrossular, Gamet is a relatively common mineral in cegionally metamorphosed igneous rocks and is also relatively common in gold deposits. Abundant spessartinerich garnets underlie the Bouquet, hunagami, Silverstack and Kewagami orebodies in Quebec (Valliant and Hutchinson 1982, ValliPnt and Bamett 1982). Garnets are Plso 8SSOCiBted with numerous gold deposits in the MeIlZies-Kambalda area of Western Australia wtt 1991). The abundant garnets in the CRLMC ace a result of metamorphism of basaltic rocks that have been subjected to extensive pre-metamorphic alaminous alteration.

3.4 Plagiocl8se Pl8gioclase in the altered cocks at the Red Lake Mine is extremely calcic (Table 3-8), Anorthite content is typically greater then An70 and ranges fmm AnU) to An93 with individual analyses ranging up to to8. Ih the Campbell Mine Pend(1996) reported plagioclase compositions ranging from An50 to An94. Plagioclase fresuently occurs as equant porphyroblasts with coospicuous radial patterns that appear similar to cyclic twinning in cordierite (Plate 3-9). Calcic plagioclase (Pl) displays bright yellow- green cathodoluminescence (Plate 3-10). The bright yellow-green cathodoluminescence (CL) results fmn either Mn2+ or F$+ which act as activators (Matshall 1988). Cotdierite under CL luminesces either red or bright blue. This makes CL a valuable method of distinguishing between cordierite and plagioclase. Reverse zoning, typical of prograde growth was detected in sample 34L-2361. Erratic compositions, varying from An50 - An89, were detected in very fine-grained (40 pm) plagioclase in sample 2413. Commonly calcic plagioclase is associated with biotitGcich alunrinous mined assemblages including andalusite, garnet, staurolite, and chlodtoid. Penaak (1996) also noted caIcic plagioclase ranging from An80 to An94 associated with biotite alteration from the Campbell Mine. Plagioclase in the least altered volcanic rocks is much more sodic (An29). EDS electron microprobe analysis indicates that anocthitic plagioclase is Table 3-8. Average electron micropbe analyses of plagiodase fmm the Red Lake Mne.

Core Rim Si02 60.98 45.99 50.73 46.34 45.13 50.3 1 46.86 A1203 Ti02 Fe203 FeO MgO MnQ cao Na20 K20 0203

Structural Formulae: Si 2.725 M4) 1.257 0.000 Ti 0.00 1 Fe3+ 0.019 Fe2+ 0.000 Ms 0.004 Mn 0.002 Ca 0.279 Na 0.696 K 0.002 Cr 0.001 0 8.000

End-Member Compositions

Xan 0.29 0.90 Xab 0.7 1 0.10 Xor 0.00 0.00 0.00 0.00 0.00 0.00 Note: n=numbcr of dyscs; Xan is the mole -ion of anoahitc; Xab is the molc fraction of albite; Xor is the mole fiadcm of otthociase uscd in thermodynamic calculations, Plagioclase is essentially unzoncd except fot Sample 34L236-1. Sample 2413 bas very cmtic compositions that vary hmAn50-An87. Plate 3-9. Calcic plagioclase (An89 with co~cuousradial extinction. The radial extinction is similer to that of cyclic twinning observed in cordierite. Mathieson (1982) mistoak the plagioclase for cotdierite. Cmparr this photomicrograph to Plate 3-6 fran Mathieson (1982). Also note the abundant porphyroblasts of staurolite (St), many of which display the diagnostic mcifimn twins* The matrix is composed almost entirely of decussate laths of biotite* Large randomly oriented pocphyroblasts of andalllsite also occur in this sample. Cross poMlight. Sample 2456. Mathieson (1982) coUection. 2gth leveL

Plate 3-10. Calcic phgioclase (Pl) displaying yellow-pen cathodolumhescence. The bright yellow-green cathodoldescence results fkom either or ~e2+which act as activators (Matshall 1988). Note the conspicuous radial pattern is still visible under CL. This may be due to varying optical orientations within the plagioclase or variations in the amount of M& or F& Cotdierite under CL luminesces either red or bright blue. This makes CL a valuable method of distinguishing between cotdierite and plagioclase. The small bright red luminescent area is &rite. Note that biotite, stamlite and andalusite in this sample do not display any laminescence and therefore, appear black under CL. The CL image was made using a Technosyn cold cathodoIDmidescence model 8200 MK-IL Operating conditions were 25 kV with a gmcmnt of 300 micro amps. Sample 2456. Mathieson (1982) collection. 24th kvel.

also common with anthophyllite-rich assemblages from the Main Zone on the 34th level of the Red Lake Mine- Calcic plagioclase has elso been reported fma a number of Archean gold deposits including Mineral Hill (Smith 1996) and numerous deposits in Western Australia (Mw11er and Groves 1991, 1991)- Certainly, i~ younger or unmetarnorphd environments plagioclase can unequivdy be interpteted as being a product of hydrothermal dteration (Atancibia and CMc 19%). The association of calcic plagioclase with duminous mindassemblages in cocks that are severely depleted in Na at the CRLMC suggests that may be of hydrothermal origin.

3.5 Amphiboles A variety of amphiboles were analysed with the electron microprobe and identified optidy including ~unmhgtonite~magnesia-hornblende, ferro-tschermakite and anthophyUite (Table 3-9). The most common amphibole is cummingtonite. Two varieties of cummingtonite were identified: 1.) Post-tectonic radiating fibrous crystals in layers that cross-cut the fabric of the rock. 2.) Randomly oriented fibrous inclusions in gamet (Plate 3- 1 1). Cummingtonite is common throughout the Red Lake Mine. Fie-grained cummingtonite in dense bands commonly co-exists with ferro-tschermakite in basaltic rocks with abundant gamet, chlorite, plagioclase and biotite. Penczak (1996) reported widespread occurrences of cummingtonite in altered rnafic volcanic mcks from the Campbell Mine. Magnesia-hornblende is commonly associated with ankerite and quartz in the matrix of cockade breccias (Plate 3-12). The cockade texture consists of a matrix of concentric layers of ankecite and quartz enveloping walhck fragments. The matrix of the breccias are composed predominantly of ankerite and quartz that is cross-cut by poikiloblastic magnesia-hornblende with abundant inclusions of ankerite, quartz, Table 3-9. Average elecwa micmpmbe analyses of amphiboks in the Red r

Amphibole 9521-1 IS-017B 26-917A 384 34L144-27 384 40.79 0.87 0.84 2.67 19.35 0.00 0.00 0.00 0.07 0.04 0.00 2.12 3.08 29. 10 24.30 30.74 19. 14 13.42 17.59 11.28 4.09 1.43 0.58 0.62 0.06 0.12 0.44 1.12 11.29 0.04 0.00 0.00 0.97 0.00 0.00 0.00 0.30 0.00 0.00 0.00 0.08 1.98 2.07 2.00 2.02 rrrrrr CIII - - 99.42 100.61 101.47 101.25

Structural formulae: Si 6.169 7.924 7.947 7.644 6.058 N4) 1.831 0.076 0,053 0.356 1.942 1.193 0.079 0.09 1 0-116 1,446 Ti 0.036 0,000 0.000 0.000 0.008 Fe3+ 0.375 0.00s 0.000 0.240 0.345 Fe2+ 2.733 3.679 2.948 3.86 1 2.378 Mg 0.776 3.O24 3.803 2.525 0.905 Mn 0.060 0.183 0.07 1 0.079 0.008 Ca 1.716 0.0 19 0.068 0.280 1.797 Na 0.350 0.0 12 0.000 0.000 0.279 K 0.06 1 0.000 0.000 0.000 0.057 Cr 0.00 1 0.000 0.000 0.000 0.009 0 22.000 22.000 22.000 22.000 22.000 OH 2,000 2.000 2.000 2.000 2.000

Name Fe-Ts Cum Cum Ath Fe-Ts Fe/Fe+Mg 0.78 0.55 0.44 0.60 0.72 3 3 6

Mg-Hbl = magnesio-b&blcnde, Cum = cummingmnite, Ahanthophyllitc. Sample 34L-144-27 from the "Main Zane." See Appendix 1 for cocxixting minerals. Plate 3-11. CPmmiagtonite inclusions in garnet. Anow points to two acicular crystals of cummingtonite totally enclosed within garnet Note the right side of the garnet contains abmdant radiating aciculaf inclusions of cmdngtonite. Other inclusions are quartz, biotite, pyrite, magnetite and ilmenite. Plane poladzed light. Sample 26-917A. 26fh leveL

Plate 3-12. Magnesiohornblende (Hbl) in the matrix of a cockade breccia with ankerite and quartz Note that magnesia-hornblende cuts across the fabric in the matrix of the breccia and does not occur in the highly altered walhck fkagments. Cross polarized light Sample 15-017B. lsth level.

magnetite and pratee The breccia ftagments consist of highly altered alpminous besalt with abundant anorthite, biotite, andalusite, stamlite, quartz and d~mortierikThe foliation in the fngnents of the bteocias are internally consistent and is the same as the foliation thmughout the CRLMC* Al~ousfeno-tschemakitic amphibole with garnet + biotite + chlorite + plagioclase (Aa29)+ ankerite + ilmenite (Sample 9521-1) was analysed from drill core at a depth of 563 feet (qaivalent to the 4& level) near the Red Lake Mine headfrarne- Very similar fe-tschermakitic amphibole was audysed from the 38th level at a depth of 5700 ft. Anthophyllite occurs in both ultramafic and basaltic rocb in the CRLMC (Mathieson 1982 and Penczak 1996). Anthophyllite was only optidly identified in ultranlafic rocks. However, anthophyllite was codinned by electron microprobe analyses in basaltic mcks enveloping the 'main Zone" on the 34th level (Sample 34L- 144-27) of the Red Lake Mine where it is quite abundant (up to 50% of the rock). It occurs as fine grained radiating acicular crystals evenly distributed throughout the mks (Plate 3-13). Commonly it occurs in bands and veins. It is difficult to distinguish anthophyllite from cmmkgtonite because the fine grain size makes it impossible to observe the twinning and extinction angles that are necessary in order to differentiate between the two. The wide variety of amphiboles in the CRLMC reflects the complexity and variability of bulk cornpsiti011~~The occurrence of anthophyllite and cummingtonite is restricted to amphibolite facie* Outside the CRLMC the badtic racks are characterized by actinolite (Andrews et aL 1986). Actinolite was not conEirmed within the confines of the CRLMC. AnthophyLlite is a common product of the isochemical metamorphism of alteration pipes associated with volcanogenic massive deposits (Eskola 1915 and Vallance 1967). However, these rock types commonly cwxist with cordierite as well as anthophyIlite and thus represent a more Mg-rich assemblage compared to the CRLMC. 3.6 Biotite Biotite occurs as fine-grained decussate laths, fibrous masses, veinlets and disseminated crystals in all rock types in the CRLMC. However, biotite is most abmdant proximal to orebearing veins where it is generally associated with Ca-rich plagioclase and ankerite. Biotite-rich assemblages often grade into chlorite-rich assemblages distally fmm -bearing veins (see section 3.15). The FeMg ratio of biotite varies between 0.36 to 0.69 (Table 3-10) aud exhibits no systematic variations within the CRLMC. However, the FeMg ratios of co-existing biotite and chIorite are remarkably Similar. The close association of biotite with ore-bearing veins and the widespread occurrence of biotite veinlets suggest that much of the biotite is of hydrothed origin (i.e. potassic alteration) and was merely recrystallized as a result of metamorphism and deformation.

3.7 Chlorite Chlorite occurs as he-grained decussate laths, fibmus masses, veinkts and disseminated crystals in all rock types. Chlorite is best developed distally from biotite- rich domains with aluminous mineral assemblages (see section 3. IS), whmit grades into biotite-rich domains (Plate 3-14). The Fe-Mg ratios of chlorite varies between 0.33 to 0.70 and closely mimics that of assodated biotite (Table 3-1 1). Textures, distribution end similar Fe:Mg ratios of chlorite and associated biotite suggest that they are re-cryseallized and re-equilibrated products of pre-metamorphic hydrothermal alteration. Biotite npnsents an early potassic alteration event that grades Table 3-10, Average electron microprobe analyses of biotite from the Red Lake Mine.

Biotite 9521-1 15-017A 2413 24-88-1 28-886-2D 34L-2361 SiO2 34.32 36.49 34.30 35.56 36.95 37.17 A1203 Ti02 Fe203 FeO MgO Mno cao Na20 K20 Cr203 H20

Structural formulae: Si 2.7 14 w4) 1.286 0.3 16 Ti 0.1 16 Fe3+ 0.121 Fe2+ 1.564 Mg 0.716 Mn 0.009 Ca 0.015 Na 0.017 K 0.882 Cr 0.001 0 10.000 OH 2.000 Fee+ Mg 0.69 *phi 0.01 12 Aann 0.1245 n 18 18 L8 18 18 6 Note: n=number of analyses: Apbl is the ideal activity of the phlogopite (Mg) end-member and Aann is the idesl activity ofthe annite (Fe) end-member used in the thennodynamic calculations. Table 3-1 1. Average electron microprobe analyses of chlorite from the Red Lake Mine.

A1203 Ti02 Fe203 Feo MsO MnO cao Na20 K20 CR03 H20

Structural formulae: Si 2.63 1 w4) 1.369 MC6) 1.359 Ti 0.004 Fe3t 0.01 1 Fe2+ 3.195 Mg 1.367 Mn 0.026 Ca 0.03 1 Na 0.002 K 0.001 Cr 0.003 0 10.000 OH 8.000

FeEe +Mg 0.70 Achl 0.00207 n 18 18 18 18 18 Note: lrumber of .D.(YscP;Xchl is the ideal activity of the clinochlo~(Mg) end-member usd ia thermodynamic calculations computed fiom the stntcturai formula See Table 4-1. Plate 113. Abundant radiating anthophyilite (Ath) in a vein with calcic plagioclase (Pl), biotite (Bt), quartz and &ritee The matrix is composed of mainly chlorite, anthophyllite, quattz and plagioclase. Cross poluized light. Sample 34L-144-27. Underground DDH 34L-144,137.99 m (453 ft). 34th leveL

Plate 3-14. Decussate laths of chlorite intergrown with and locally enveloping biotite Qt). Note that this is not a retrograde replacement of biotite by chlorite, but rather a coeval intergrowth of the two mineds. Biotite-rich assemblages commonly grade into chlorite-rich assemblages distal to mineralization. Plane polarized light. Sample 38-5. Underground DDH 38-02.639.07 rn (2098 ft). 38th level.

laterally into a distal chlorite-rich assemblage. Contrary to Colvine et al. (1988), chlorite does not repsent a later setrogndt metamorphic event.

3.8 StauroUtc StauroIite is restricted to highly altered basaltic rocks in the Red Lake Mine- It was also observed 2.5 hn east of the Red Lake Mine in anza defied by MacGeehan and Hodgson (1982) as a perdprninosity (A/CNK) anomaly (Sampk BR-1). Within the Red Lake Mine, staurolite first appears on the 15th level in the wallrocks of the SCaezone and persists to the deepest levels sampled (38h level). Stamlite has not been observed in the Campbell Mine (Penczak 1996). It occurs as syn- to post-tectonic porphyroblasts commonly associated with plagioclase, biotite, chloritoid, andalusite and garnet (Plate 3- 15). Staurolite within large cotdierite porphyroblasts was obsedin ody one location (34th level of the Red Lake Mine) in association with margarite, muscovite and andahsite (Plate 3-3). Porphyroblasts commody contain abmdant inclusions of quartz, plagioclase, ilmenite and magnetite. The chemistry of staurofite is typical of most analyses with a high FelFe + Mg ratio (Table 3-12). An interesting fature is the variable Za content in staumLite. The zinc content of staurolite varies hm0.28 to about 5.4 weight percent ZnO (Figure 3-2). Note that XFCis lowest in the staurolite with the highest Zn, a correlation also noted by Fox (1971). There is also a strong correlation between ZnO and apparent Na20 in staurolite (Figure 3-2). Staumlite is the only silicate mineral which readily incorporates zinc into its crystal structure because it favors substitution of Zn2+ over M$+ in place of Fe in the sites that are tertahedrally coordinated with oxygen (KoUister 1970 and Deer et aL 1982). Zincian staurolites are not uncommon and have been reported in a number of geological settings (Ashworth 1975, Atkin 1978. Leclau 1982, ZPleski et al. 199 1). The variable zinc content in staurolite appears to be related to its modal abundance and possibly to metamorphic grade. The highest values for ZnO occur where Table 3-12. Average e1cctron xnimpmbc analyses of staurolitc hrnthe Red Lake Mine.

Fe/Fe+Mg 0.82 Ast 0.2282 n 12 18 18 18 6 Note: nmumbcr of aualyscs. Formula based on 46 catioaic charges. Ast is the activity of Fe-staumlite used in thermodynamic calculations, basEd on 92 cationic chacgcs, in order to be compatible with Beiman (1991). ZnO Versus Apparent N40 in Energy Dispersive Spectrometer Analyses of Stawolite

Figure 3-2. Graph exttapo1ates a bear coneletion between apparent N40 and analysed ZnO in starnlite so as to enable estimation of weight percent ZnO fktn the apparent weight pacent N%O in a "standard" lklement microprobe analysis. Because the zinc La pak virtually coincides with the sodium K$ peak, the standard analytical setup misinterprets the zinc in staumlite as sodium. Note that there is almost a 21ratio between measured N40 and ZnO. The samples represented by squares were measured separately fbr N40 and ZnO. The circle repmsent the sample that was measured br N&O only. Sample 34L-2364 was analysed fir NqO only. The measured NhO corresponds to about 5.5 weight peccent ZnO. staorolite is least abundant in thin section (5%). This suggests that whole rock zinc maybe similar in the analysed samples, with the zinc content of stamlite being diluted as moce stamlite crystames. StamIite is u~ownin metamorphosed igneous rocks of normal composition (Deer et al. 1982). Its occurrence is restricted to igneous mcks which have undergone intense metasonlatima (Beach 1973). Within the Red L.ake Gieenstcme Belt, staurolite is present in the Madscn Mine and the Starrett-Olsen Mine (Dtuocher 1983).

3.9 Chloritoid Chloritoid is abundant throughout the CRLMC. It occurs mainly in altered basaltic rocks, but it also occurs in rhyolite, dioritt and sediments at surface as well as underground and up to 2.5 km east of the Red Lake Mine. Chloritoid was observed throughout the Campbell Mine (Penauk 1996) and down to the 34th level of the Red Lake Mine. However, it has not been found in samples from the 38th level. Chloritoid generally occurs as syn-kinematic radiating porphyroblasts with biotite and staurolite. Commonly, chlotitoid displays polysynthetic twins typical of the triclinic polymorph (Deer et aL 1982). Rarely, cblocitoid occurs with syn-kinematic sygmoidal inclusion trails of quartz and ilmenite. Chloritoid observed in sediments from the l6h level at the Red Lake Mine displays both syn-tectonic and post-tectonic porphymblasts (Plate 3-1). Chloritoid is iron-rich (Table 3-13) and the high FelFc + Mg ratio is similar to that of co- existing staurolite: 0.88 and 0.85, respectively. Chloritoid is not an unusual mineral in altered volcanic rocks. It has been desscribed in mafic volcanic rocks by Simpson (1937) and Rider (1947) fmm Kalgoorlie, Western Australia It also occurs in lenses of pyrophyllite at the Womble Mine in North Carolina in altered Ms.dacites and rhyolites (Stuckey 1926). Gustafson (1 946) reported chloritoid in ankentized mafic volcanics from the Hollinger Mine, Ontario. Chlocitoid has also been reported fiom the Harvey Hiu and BmeMines in Quebec by Milne (1949) and by Cornwall (1955), rrspectively. It occurs along with otber dominous minerals at a number of other gold deposits throughout the world including, Casa- Berardi in Quebec (Pattison et aL 1986), Crixas in Brazil (T&omson 1986) and the Hope Brook and Cbetwynd deposits in Newfoundland (b4cKenzie 1986).

3.10 Andalusite The only aluminosilicate polymorph in the CRLMC is andalusite. Andalusite occurs in sedimentary rocks, as well as altered felsic and basaltic rocks throughout the entire CRLMC. Andalusite occurs in two different habits, commonly in the same thin section: (1) Latekinematic anhedral poikiloblasts that overgrow the fabric in the rock which is defined by ilmenite and quartz inclusions (Plate 3-2). (2) Fine-grained euhedral crystals in deformed quartz veins (Plate 3-16). The second paragenesis implies that andalusite may have crystallized hmpyrophyllite veinlets via the reaction: PyrophyUite r Andalusite + 2 Quartz + Hz0 Microprobe analyses of andalusite indicate that it is almost pure with only minor amounts of ~e2+(Table 3-13). This is consistent with the lack of pleochroisrn in thin section. Andalusite occurs in altered volcanic rocks associated with gold minetalization in many different mines ranging in age From Archean to Paleozoic. I.the Red We Greenstone Belt, andalusite has also been sported from the Campbell Mine (Christie 1986, Penczak 1996) and Point Rock near the Cochenom-Wrllans Mine (Ferguson 1968). Andalusite and sillimanite occur in tsmples from the Smrrett-Okn Mine (Queen's University Petrography Collection). Ansdalusite is abundant in the Big Bell, Sons of Mate 3-15. Latetectonic staurolite (St) and chloritoid (Cld) porphpblasts. Stettrolite overgrew the foliation of the rock defiaed the alignment of ow,tabular ilnrenite and clear, fibrous macgarite @dig) crystals adwas subsequently rotated dextrolly by only about 150. The foliation strikes E-W across the photomicrograph. Radiating sheaf of chloritoid is in sharp contact with staurolite. Phe Sample 157-18. Mitthieson (1982) collection. 23RM level lisht,

Plate 3-16. Euhedral andalusite (And) porphytoblasts in a deformed quartz vein. This vein may have originally been composed of pyrophyllite prior to metamorphism. Vein cuts across the foliation and is boudkaged. This altered basalt is compused of garnet (Grt) porphyroblasts with a matrix of staurolite, biotite, chlorite, plagioclase, quartz, andalusite, anketite, apatite, tourmaline, ilme~teend magnetite. Plane polarized light. Sample 28-886-21). 28th level.

Gwali. and Mount Celia deposits in Western Australin (Chown et aL 19&1; Ride 1990). the Paleozoic Carolina Slate Belt (Ririe 1990) and the Chetwynd deposit (Hope Bmk Mine) in the Appbchians ofNewf001lm (McKenzie 1986). The Hemlo deposit contains both kyanite and sillimrnite indicative of higher pressure metamorphism (BllrL 1987; Kuhns et 11 1994). Ib all cases the aluminosilicate polymorphs may be intetpreted as arising from metamotphisrn of alpminous alteration assemblages (Chown et aL 1984; Ririe 1990; Johnston 1996 and Penczak 1996).

3.11 Muscovite Muscovite is not as common as the other phyllosilicate minerals in the CRLMC. Muscovite is distinguished from sericite by its coarser grain size (generally >Sop). Representative analyses of muscovite are given in Table 3-13. Muscovite is commonly associated with altered felsic rocks that have abundant margarit. and andalusite with lesser amounts of chlorite, biotite and cordierite and stawlite (see Plate 3-3). Muscovite grains up to 200 pm are present in orebearing quartz-snkerite veins associated with biotite. It also occurs proximal to the ore-bearing vein structures with biotite and ankerite (see section 3.15). Late fine-grained sericite pthilyreplaces plagioclase phenocrysts in the QFP dykes. Muscovite is not associated with aluminous alteration minerals in basaltic rocks from the Red Lake Mine and has not been observed coexisting with garnet. Muscovite is interpreted as a prograde metamorphic mineral and not as a later retrograde mined as suggested by Colvine et aL (1988). The distribution of muscovite is controlled by bulk composition and hydrothermal alteration around ombearing vein structures. Muscovite is a common alteration mineral at the Campbell Mine in dtramafic rocks with cordierite and in the inner "bleached"zone in basaltic rocks with andalusite and quartz (Penczak 1996). 3.12 mk Margarite is commonly found in altered sediments frora the 15th level and felsic rocks from the 34th in the Red Lake Mine. It is rarely found in altered basaltic rocks. Microprobe analyses of margarite (Table 3-13) in febrocks fnrm the 34 Level of the Red Lake Mine are very simhto the analyses reported by Pen& (19%). Margatite commonly occurs as very fine (40pm), aciC0181: crystals intergrown with muscovite that define a weak foliation (Plate 3-17AIB). Margarite is distinguished optically from muscovite by its higher nlief and lower birefcingence. Christie (1986) and Pen& (1996) documented margarite in altered basaltic rocks fmm the Campbell Mine. Marganite in the CRLMC may have formed frnn a Ca- bearing clay (e-g. Ca-montmorillonite) alteration in basaltic rocks as suggested by Penczak (1996).

3.13 Coderite

Cotdierite is not as ab~dantin the Red Lake Mine as was pnviwsly thought. Mathieson (1982) and Mathieson and Hodgson (1984) commonly misidentified plagioclase as cordierite (Compare Plate 3-9 hrnthis study to Plate 36from Mathieson 1982). This was confirrued by microprobe analyses ofthe same samples (ie. 2456) originally described Mathieson (1982). Cordierite was confinned by electron microprobe analyses only in felsic rock fiom the 34fi Level mble 3-13), where it is associated with quartz, margarite, muscovite, chlorite, plagioclase and staumlite (see Plate 3-3). Microprobe analyses indicate that cordierite is hydrous and has Fe:Mg ratios similar to those reported in the OrijWi region, Finland (Deer et al, 1978). Christie (1986) and Penczak (1996) have reported cotdierite in altered basaltic rocks and ultramatic rocks hmthe Campbell Mine. Cordierite-anthophyllite rocks are commonly believed to have resulted from the isochemical metamorphism of chlotitic alteration zones associated with VMS deposits Plate %HA. Mkrgarite (Mrg) in metasdhent with mpscovite (Ms), quartz (Qa) and opaque ilmeaits Note that margarite is distinguished from mpscovite by its lower birefkingence and higher relief. Muscovite displays second order yellows, g~msand blues and mergarite displays titst order yellow. Ibhthieson (1982) had mistaken margarite in this sample for Siuimanite. Also note the detrital po1ycrystalrine aggregates of quartz. Cross polarized light. Sample 118-31. hrlathieson (1982) coUection. 23d level

Plate 3-17B. Layer of crenulated macgarite (Mig) enveloping a porphymblast of andalusite (And) and a polycrystalline aggregate of quartz (w).Matrix is composed of very fine-grained (40 pm) quartz, plagioclase, muscovite, chlorite and ilmenite. Cross polarized light. Sample 118-3 1. Mathieson (1982) collection. 23d level.

Table 3-13. Average e1ectton miccopmbe analyses of chloritoid, andabsite, cordierite, muscovite and margarite fiom the Red Lake Mine.

ad And Crd Ms 2413 24-88-1 28-886-2D 15417A -236-1 34-1 34G234-I

A1203 Ti02 Fe203 FeO MgO M.0 CaO Na20 K20 Cr203 H20

Structural formulae: Si 2.060 AK4) 0.000 A-W) 3.896 Ti 0.001 Fe3+ 0.000 Fe2+ 1.702 Mg 0.269 Mn 0.047 Ca 0.003 Na 0.003 K 0.003 Cr 0.008 0 10.000 OH 4.000

wte.- "~"zcf& to the activities CIQ And, Ccd, Mi and hkg tcspcctively, usd in therrmodynamic calculations (Set Table4-1). (Eskola 1915, Vallence 1967). However, in the CRLMC, COZdierite is commoaly associated with alpminous alteration (Pend 1996).

3.14 OtkMined There are numerous other minerals in the CRLMC that indicate the aatnre of hydrothermal alteration and metamorphism. They inclu& rare occumnces of dumortierite, scapolite and scbeelite. In the Red Lakt Greenstone Belt, dmortierite has been observed only in the Red Lake Mine (Mathieson 1982, Lavigne 1983). Dumortietite was observed in ore from the South C ore zone and the ESC ore zone wherr it commody occurs as very fine-grained fibrous pink-purple pleochroic grains (Plate 3-18 and 3-19). It is commonly 8SSOCiated with other aluminous minerals including garnet, staurolite, chloritoid, andalusite and tounnaline. Dumortierite is commonly associated with advanced argillic alteration (aluminous mineral assemblages). Typically, the formation of dumortierite relative to tourmaline is favored where concentrations of Fe, Mg, Ca and Na are low, possibly due to leaching of alkalis prior m the addition of boron. At the Red Lake Mine, the presence of damortierite may be a mineralogical expression of acid metasomatism associated with gold minetalization. Dunortierite also occurs at Louvicourt, Quebec mer1993, Taner and Mania 1993), the Big Bell Au deposit in Western Australia (Chown et aL 1982) and the Chetwynd Au deposit in Newfoundland (McRenzie 1986).

3.15 Mineralogical Protile of the "Main Zane" on the 34th Level The "Main Zone'' on the 34th Ievel of the Red Lake Mine is one of a set of recently discovered high grade (up to 421 oelton over 0.6 h) ore zones. The ''Main Zone" is a quartz-carbonate cockade breccia zone with fissure veins in altered basaltic rocks that are Plate 3-18. Damortierite @om) and biotite @t) intergrown with otebeadng arsenopydte, pydte, and magnetite Emn the East South F om zone. Dumortietite displays characteristic purple pleochroism. Clear crystaIs are quartz aad plagioclase. Plane polaeiztd light Sample 2471. Mathieson (1982) collection. ESC a 241h leve~

Plate 3-19. Purple pIeochroic dumortierite @pm) with staurolite (St) end biotite (Bt) in highly altered bdtfragment of a cockade bdaThe char crystals are quartz and plagiocIase. Note that plagioclase has slightly higher dief than the quartz, The opaque minerals ate magnetite and ilmenite. Plane polarized light. Sample 15-017B. 19level. overprinted by grey siliacation (R Pen& pets. canm. 1996). Mineralization consists of acicular arsenopydte with local disseminated pyrite as well as magnetite and visible gold, Arsenopyrite wall-mck replacement rninetalization occurs in both the hangingwall and footwall. Thirty-two thin sections fkom diamond-drill hole 34G144 were examined in onier to characterize the nature and distribution of mineral assemblages in the hanging wall and footwall of the "Main Zone." It is apparent that three distinct zones are developed almost symmetrically around the "Main Zone" (Figure 3-3). The maximum- phase mineral assemblages in the three zones are listed below in order of abmdance of the minerals present= (l)Chl+Pl+Ga+And+Qa+St+Cld+Bt+Ilmf Cmn@istal) (2) Hbl + Bt + Chl + P1+ Qtz + Ank + Mt f Ath (Tntemediate) (3)Bt+Ank+Qa+Ms+Pl+Mtf Chl (J?roximal) The distal assemblage is characterized by abundant aluminous minerals. Radiating fibtoos cummingtonite occurs only in distinct Layers with garnet (Plate 3-20). The most abundant mineral is Fdchchlorite. Plagioclase is locally abundant with patches made up almost entirely of plagioclase and chlorite with biotite* Biotite-rich domains grade outward to more chlorite-rich domains. Staurolite and chloritoid are most abundant in biotite-rich bands. S~aumlite+ chlositoid + plagioclase + quartz + chlorite occur also in peculiar ptygmatic veins in a garnet + Fecblodtsrich basalt (Plate 3-21). Andalusite occurs as very fine grained (QO pm) disseminations throughout the matrix. Local patches of grey basalt are composed almost entirely of andahsite, quartz, muscovite and ilrnenite. Patches of "bleached"basalt are more abundant in the footwall. This is also evident fkom Figare 3-3 which shows discontinuous development of aluminous assemblages in the footwall. Ankerite is rare (4%).Magnetite and ilmenite are the only oxide minerals.

Plate 3-20. Layer composed almost entirely of euhedral garnet (Grt) and fibrous cUIIlZlJingtonite in the distal alteration wne enveloping the "M;ain Zone" at the Red Lake Mine. Note that the garnets luve ioclusion-dch cons and clear rims similar to Plate 3-7. Plane polarized light. Sample 34L-144-1B. Undagomd DDH 34G144.86.20 m (283 ft). 34th 1eveL

Plate 3-21. Peculiar ptygmatic vein in the distal alteration zone of the 'Main Zone" of the Red Lake Mine. The vein is compdsed of cloudy, light brown calcic plagioclase (Pl), poildloblsstic andalusite (And), radiating bundles of chloritoid (Cld), tabular stamlite (St) and clear quartz near the vein margin on the left band side of the photomicrograph. Vein also contains traces of chlorite aad biotite. The host rock is composed almost entirely of iron-rich chlorite with large (up to O.Scm) porphyroblasts of garnet with cummingtonite and ankerite inclusions. Opaque minerals are pt6dominantly ilmenite with lesser amounts of magnetite. Plane polarized light. Sample 34L-144-25. Undergmmd DDH 34G144,134.94 rn (443 a).34a leveL

The intermediate assemblage is chanlctedzed by abundant hornblende aacf anthophyllite (Plate 3-22). Rocks with abundant hornblende tend to have lesser amounts of rnthophyllite with modal calcic plagioclase (bytowrite-anorthite) remaining relatively luriform near 10%. ranging up to 3096 in local patches. Biotite becomes gradually more abmdant than chlorite towads the '%binzone". Ankerite incresses gradudy to 5-1046. Magnetite is the most abmdant oxide phase with lesser amounts of ilme&. The proximal assemblage is dominated by biotite and &rite with mallet amounts of muscovite and quartz (Plate 3-23). Chlorite and plagioclase am rare (~2%). Amnopyrite, pyrite and magnetite are the dominant opaque phases with trace amounts of pyrrhotite and chalcopyrite. Biotite occurs as finegrained (20-50pm) decussate laths throughout the matrix and in veins obliqoe m the foliation with ankerite and sdphides. Ptygmatic veins of tomaline are also present proximal to the "Main Zone." The zoning of mineral assemblages mund the 'Main Zone" at the Red Lake Mim is inferred to represent metamorphism of hydrothermal alteration. The outer zone, dominated by low-variance aluminous assemblages, is inferred to have formed from a protolith rich in kaolinite (i.e. a zone of advanced argillic alteration). Local domains ("bleaching") within this zone are composed almost entirely of andalusite, muscovite, quartz and ilrnenite. The intermediate zone, dominated by 8mphiboIes and chlorite, may have formed from a chlorite-rich protolith (i.e. a zone of chloritization or possibly intermediate argillic alteration). Close to the o~rebeatingstructtm, the proximal zone is infed to have formed from a protolith rich in biotite, muscovite, quartz and &rite (Le. a zone of potassic alteration). During metamorphism, hydrothermal biotite, muscovite, chlorite, quartz and ankerite are inferred to have recrystalli;rPrl and re- equilibrated with newly formed minerals such as gamet, staumlite and chloritoid, whik the lower ternperamre hydrothermal clay minerals in the outer wne were completely replaced by the newly formed minerals. Plate 3-22. Blocky and diamond-saped crystals of magnesi~~homblende(Hbl) and fibrous anthophyllite (Ath) in the intermediate alteration zone of the "Main Zone" in the Red Lake Mine. Finegained matrix is composed of quartz, calcic plapiochse and ankcrite. Opaque minerals are precfdtlymagnetite with lesser amounts of ilmenite. Cross polarized light Sample 34L144-8. Underground DDH 34G144,104.18 m (342 ft). 34th leveL

Plate 3-23. Equigranular intergrowth of biotite, ankerite and quartz and opaque minerals in the proximal alteration zone of the "Main Zone" in the Red Lake Mine. Grain boundaries are sharp and commonly display graaoblastic polygonal texture. Opaque minerals are predominantly arsenopyrite with lesser amounts of pyrite and magnetite. Cross polarized light. Sample 34L-144-15. Underground DDH 34L-144,115.29 m (378.5 ft). 34th IeveL

3.16 SlpMkance at the Tdtionfmm Chloritoid- to StauroUte-bearing AssembIages ChIotitoid and stamlite have similar composition, with staurolite being somewhat more aluminow and less hydrous. With inmaskg metamorphic gRde there is commonly a transition from chloutoid-bearing to stamlite-bearing assemblages (Turner 1981). The CRLMC and nearby sd&e exposures provide access to this metamorphic transition in thne dimensions. The transition ftom chloritoid-bearing assemblages to stamlite-bearing assembalges is shown on the schematic cross-section of the Red Lake Mine (Figure 34), the sarfke map of Balmer Township (Figure 3-5) and

the composite levels plans of both mines at a dcpth of about 640 meters fmm the surf" (Figure 3-6). The staurolite-in isograd is based on the first appearance of stamIite on the 15th level of the Red Lake Mine. The chloritoid-out isograd is based on the disappearance of chloritoid below the 34th level of the Red lake Mine. The isograds strike roughly north-south (e.g. N20OW) and dip westerly at 300. The dip of the isograds can be roughly calculated fnn figures 3.5 and 3-6. The vertical distance between the two isograds is approximately 880 m. Hence, the true thickness of the stawolite + chloritoid "zoneof persistence" is 760 m (880~0~300).This may imply that the Walsh Lake pluton has a shallow dip beneath the CWC. A gravity survey by Gupta and

Wadge (1986) seems to support this inference. The total vertical depth of samples is only 1.75 km (5700 ft), which is equivalent to only 0.5 kbars. Therefore, the transition from chloritoid-bearing to staumlite-karing must be due to an increase in temperature. Staumlite is typically formed from chloritoid-bearing assemblages via the reactions: (1) 23 Chloritoid + 2 Quartz = 2 Stamlite + 5 Garnet + 19 Hz0 (2) 8 Chloritoid + 10 Andalusite = 2 Staurolite + 3 Quartz + 4 H20 (3) Gamet + Chloritoid + Andalusite = StaumIite + ~uartz+ Hz0

htonndiatebf.hlc \\ Wank Rocks \ MakVdanic Rodis 4

Figure 3-5. Geology map of Balmer township showing the locations of the greenschist/amphibolite facies isograd as defined by Anbws and Wallace (1983) and Andmws et al. (1986). Modified after Pirie and Grant (1978), MacGeehan and Hodgson (1980), Atkinson and Stone (1993) and PennaL (1996).

Inc1usions of chloritoid in garnet with stamlite in the matrix suggest that reaction (1) has occrmd in some of the rocks. Statuolite-only assemblages become more abundant leading up to the chlolitoid-a~t&grad. d. chloritoid-out isogrPd occurs between the 34a and 38& level ofthe Red Lake Mine (Figare 34) and may be related to the reaction: (4) Chloaitoid = Garnet + Chlorite + Staurolite + Hz0 The association of stamlite with chloritoid is prevalent throughout the CRLMC suggesting that chloritoid was a progenitor of stamlite. In low-pressure regimes staurolite ~otxunod~cuexistswith cordierite rather than garnet (e-g. Sample 34L-236-1). Samples of cordierite and stamlite in textural equilibrium are found in the deeper levels of the mine, indicating chat low pressure assemblages are fomd throughout the CRLMC (see Plate 3-3). The presence of staptolite inclusions in cordierite with abundant andalusite suggests the reaction: (5) 2 Stawolite + 15 Quartz = 4 Cordieate + 10 Andalusite + 4 Hz0 Stamlite is also commonly in textural equilibrium with biotite and chlorite. Many reactions can be devised from such assemblages. The appearance of staumlite was brought about by a variety of different reactions. The reactions presented above only represent five possibilities based on less ambiguous textural evidence.

3.17 Discussion Mineral assemblages characteristic of mafic rocks are very rare in the CRLMC- The characteristic assemblage of mafic rocks in the upper greenschist facies is actinolite + Mgchlorite + quartz + epidotdzoisite + albite t carbonate (calcite, dolomite or ankeri te) t titanite and the characteristic assemblage in the arnphibolite facies is hornblende + oligoclase t quartz t he* (Spear 1993). The transition from greenschist facies to mphibolite f&es in mafic mks is marked by four mineralogical changes: (1) PlagiocIase changes fmm albite to oligoclase across the peristerite gap. (2) Amphibole changes from actinolite to hornblende through the addition of A1 + Na (3) Chlorite becomes incrashply Mg-rich and eventually disappears. (4) Epidote deneascP in abmdance and eventually disappears. Only changes (1) and (2) have been recognized in the altered basaltic rocks from the CRLMC Near the hadfhme of the Red Lake Mine, the assemblage Gtt + Hbl + P1 (An 29) Qtz + Chl + Bt + Ank + Ilm (Sample 9521-1) is diagnostic of amphibob fkies. Underground the least altered basaltic mck contain the mineral assemblage Hbl + PI (An90) + Chl + Bt + Qtz + Ank + Llm (Sample 29-877 SXC). However, both rocks are too potassic to has been derived from a normal bdticpmtolith.

Although superficially some of the rocks in the Red Lake Mine appeat to have pelitic bulk composition it is clear that they are not metapelites but altered metabasalts.

Primary volcanic stroctares and textare (piUows and varioles) are preserved in highly altered basalt and even in ore (Lawe 1983). The plagioclase is much more calcic than in normal metasediments and even normal metabasites. Muscovite is rare compared to metapelites. Due to extensive pre-metamorphic hydrothermal alteration, varying metamorphic conditions and the wide variety of bulk compositions (i-e. rock types and alteration) a diverse set of mineral assemblages have been preserved in the CRLMC. The mineral assemblages preserved in the CRLMC demonstrate the transition from greenschist to mphibolite fdes assemblages in weakly altered basaltic mcks occurs before the staurolite-in isograd in highly altered basaltic rocks (essentially pelites) with alminous assemblages. The Red Lake Mine is not transected by a greenschisVamphibolite facies transition as suggested by Andrews and Hugon (1985) and Andrews et d. (1986). Instead, the staurolite-in isograd strikes roughly N2WE and transects the Red Lake Mine underground at about the 15th level The oae constraining sample on surface is 2.5 km east of the Red Lake Mine. This requires that the dip of the isograd to be 300 to N6CPW. Therefore, it is clear that the isograd aoss-cuts the dominant stmcturai "grain" and the set of alteration zones that surround the on at the CRLMC. The low-variance alpminous assemblages are inferred m have fonned by the metamorphism of a previous high-variance alteration assemblage rich in clays. The metamorphism need not have been strictly isochemical, but it must have been rock- dominated rather than fluiddorninated. By contrast, the drastic chemical changes reflected in the alteration zoniug can have only occurred in a fluiddominated system. In metasomatic environments the system is considered to have been open with the removal and addition of elements. These mobile elements are contrdled by parameters external to the system (ir infiltration) and result in relatively few alteration minerals (Rice and Ferry 1982) like those common in skams. Consequently, in the metamorphic environment the system is dominated by parameters internal to the system (i.e. baering) and low-variance assemblages form because the system is controlled by parameters such as water activity (Greenwood 1975). At the CRLMC the low-variance assemblages are restricted to mivariant lines in P-T space and commody even invariant points. If the system was dominated by infiltration of fluid, low-variance assemblages should be non- existent. Therefore, internal buf5ering must have been the dominant physicofhemica1 control on the crystallhtion of the low-variance assemblages at the CRLMC. The only way to generate the low variance assemblages observed in the CRLMC from high variance assemblages is to overprint the alteration assemblages by metamorphism. 4. Themnobarometry and Fluid Composition

4.1 Iatroduction Accurate assessment of the temperatores and pressures under which metamorphic mcks have formed is an important goal of modem petrologic stndies. Presswe and temperatore of metamorphism are vital to our understanding of the chemistry not only of metamophic processes, but also of the tectonic proasses invoIved In order to determine the peak pressure and temperature under which a rock sample fonned, two critical assumptions must be made:

(1) the rock closely approached thermodynamic equilibrium at the maximum temperature of the metamorphic cycle, and (2) the coexisting minerals did not change composition during cooliag and exhumation d the sample. Petrographic evidence, data showing a regular partitioning of elements among coexisting minerals, and intra- and inter-sample consistency are most commonly used to argue for the attainment of equilibrium (Zen 1963, Vernon 1976,1977, Spear 1989), but all such evidence is permissive; there is no way to prove equilibrium At equilibrium for any mass-balanced reaction involving "pure" endmember chemical species in coexisting minerals, the fbndamental equation that describes the formal thermodynamic relationship among pressure, temperature and the activities of the species in the minerals is given by: where Vi is the coefficient of species i in the balanced reaction (taken as negative for a reactant species), and q is the activity of species i relative to unit activity for the pure species i at equilibrium P and T. The terms AG, a AS, AV, ACp, are known as the free energy, enthalpy, entropy, volume and heat capacity of reaction each of which express a difference between the reactant and product sides of the reaction, with reactants taken as negative. R is the gas constant, At eqdibcim, the free energy of reaction must be zero. Oood geothemometers ate those reactions that show considerable temperature sensitivity (large AH and AS) and small pressure sensitivity (small AV) and good geobarometecs are those reactions that show significant pressure sensitivity (large AV) and small temperature sensitivity (small AH and AS). In a thennobarometric calculation the set of simultaneous values of P and T that satisfy equation (1) must be determined because AV is a bction of P and ACp is a

function of T. Furthermore, because ai for some species is a finction of P and T, equation (1) can be solved conveniently only by computer iteration. Generally, ai is a fhction of P, T and X, but experimentally determined P-T-X activity models are available and have been used for garnet, plagioclase, biotite, cordietite and muscovite. For the other minerals, activities are assumed to be a function of X (composition) only, in accord with the "ideal' activity-composition relationships in Table 4-1. The values for AH, AS, AV and ACp are computed fnna a themodynamic database (e-g. Berman 1988). The coexisting minerals in each sample of rock are chemically analysed using the electron microprobe, and from the calculated structural formulae the values of the activities of each end-member species are determined. For each mass-balance reaction, the set of paired P-T values that satisfies equation (1) defines an equilibrium curve on a P-T diagram. Equilibrium curves for two such reactions may intersect so as to define a unique P and T of apparent equilibrium. Rocks samples to which more independent reactions are pertinent provide a check for internal consistency, because at equilibrium, all independent equilibrium curves must intersect at the same P-T point Two computer pmplg~llswere utilized in order to calculate the pressures, temperatures and activity of Hz0 at which the rocks in the Campbell-Red Lake Mine Complex (CRLMC) eqdibrated: (1) TWEEQU (Thermodynamics With Estimation of EQUilibrium) ftom Berman (1991) (2) WEBINVEQ (WEBsite with mewEQuations) utilizing the method of Gordon (1992) The TWEEQU computes P-T curves for allpossiie equilibria implied by a given mineral assemblage using an internally consistent set of thermodynamic data for end members, mineral species, fluid species, and activity models and mixing properties man1988; updated 1990 and 1996). The activity-composition models used are presented in Table 4-1. It has been shown that the convergence of all equilibria at a single P-T-X eoncoirelates well with textural and chemical indications of equilibrium (Bern 1991). Rock samples were selected for analysis with the maximum number of minerals in apparent textural equilibrium, so that the maximum number of independent reactions would be pertinent to them and would thus provide the most reliable P-T estimate and the best possible evidence for its reliability. The WEBINVEQ program uses the TWQ 1.02 thermodynamic database of Bennan (1988) with updates by Berman (1990) and Berman and Aratrovich (1996) to compute a P-T estimate based on the inverse chemical equilibrium method of Gordon (1992). WEBINVEQ is maintained by T.M. Gordon at the University of Calgary and is accessible via the internet at httpJ/ichor.geo.ucaIgary.ca/-tmglwebw Chloritoid was provisionally added to the WEBINVEQ data base using the FEB90.RGB version of Beman (1990). The inverse chemical equilibrium problem is the determination of unknown equilibrium pressure, temperature and chemical potential of all mineral species, given measurements of their thennochemical constants and the compositions of phases in which they occur (Gordon 1992,1994). Graphical output is in the form of an ellipse which repntsappximately a 70% confidence region under the assumption that errors ue normally distributed with standard deviations cotte~pondingto about 10% emr in end-member activities. it is important to note that WEBINVEQ computes equilibrium curves only fm reactions that are independent of the activities of the volatile species in the fluid phase.

Table 4-1. Solution models and activities used in the computation of equilibrium cums. Note that TWEEQU and WEBINVEQ use different P,T Xdependent solution models for garnet and that WEBINVEQ does not use a P,T Xdependent solution model for cotdierite.

Garnet (WEBINVEQ) (Berman 1990) Cordierite ('IWEEQU) Biotite (Bennan and Aranovich 1996) (McMullin et al. 1991)

Hornblende Muscovite wider and Berman 1992) (Chatterjee and Fmese 1975)

Plagioclase Chlorite clinoctrlore (Fuhrman and Lindsley 1988) 14.93 [~g]~[A.l]

Staurolite ~e]4 Cordierite wg]2 (WEBrnQ) Andalusite [All2 Note The activity of Si% in quartz is assumed a be unity. 'Ibc cliaocblom activity cxpcssicm assumes complete disotdcribg of Mgand Af on the six odwdral sites in the structutal fmulae. AJl cxphssions assume clcctrostatic coupling of cationic substitutions in the tetrahedral sites to the octahedral and larga sites. [a] is the mole fiaction of vacancies hthe tbiml octabcdral site in margaritc.

4.2 Analytical Methods Mineral analyses were performed on an ARL-SEMQ electron microprobe st Queen's University supervised by &A. Jamieson, using an energydispersive spectrometer (EDS). Operating conditions were maintained at an accelerating voltage of l%V, a beam current of 40nA and a beam diameter of approximately 2 m. The primary standard used fot all analyses was glass NBS 470 (National B~ucauof Standards). Mineral compositions listed represent an average of at least thnc analyses from the corn and dm of three separate pinsin textural eqtdi'brium counted for 100 seconds. For minerals with appreciable zoning Qamet and pIagioclase), the core and rim compositions were not averaged and only the rim compositions wee used in thermodynamic analysis. In all cases three separate pups of mineral grains within 1- 2mm of each other were analysed from different areas within the same thin section. Data redaction was completed according to the procedure of Bence and Albee (1968) using the correction coefficients of Albee and Ray (1970) as modified by P.L. Roeder (Queen's Universify). Stmctural formulae and ideal activities were calculated using the APL computer program MINPROBE developed by D.M.Carmichael (Queen's University). Ideal activities and stmctluai fonnuiae calculated were then used in TWEEQU and WEBINVEQ to generate P-T-X diagrams.

Pressures and temperatuns wen calculated throughout the Red Lake Mine using four different low-variance assemblages. Five altered basaltic cocks and one altered felsic rock were chosen for themobammetric analysis. Three separate assemblages were analysed in the altered basaltic rocks, all of which include quartz: (1) Grt + Hbl + Bt + Chl + P1+ Ank + h (Sample 9521-1) (2) Grt + Bt + Chl + Pl + Cld + St + And + Ilm (Samples 2413 and 24-88-1) (3) Grt + Bt + Chl + PI + St + And + Mag -t Ilm (Samples 15-017A and 28-886-2D) The low-variance assemblage in the altered felsic rock consists of: (4) P1+ Crd + Bt + Ms + Mrg + St + Chl + Ilrn (Sample 34L-236-1) All samples selected for thennobarnmetry appear to be in textural equilibrium (i.e. individual minerals analysed had relatively sharp gRin boundaries, granoblastic textures, lacked secondary alteration minedand occur in the same domain in the thin section). Mine& in domains isolated from the other minerals ae. Cum inclusions in Grt) were not used for themrobammetry. Although chloritoid is present in samples 2413 and 24-88-1 it was not used in thermodynamic calcuiations because the thermodynamic pooperties are not well constrained by availabIe phaso-eqpilibrium experiments (Berman 1988). When chloritoid is used in TWEEQU,93 equilibria are plotted with 5 independent reactions and extremely wide scatter (Figme 41). However, when chloritoid is removed only 35 equilibria am plotted with 4 independent re8~tionsand the equilibria converge around an area fmm 1200,2000 bars and 48m(see Figure 44). Well constrained P-Testimates were obtained hmthree of the altered basaltic mcks (Samples 1S-O17A, 24-88-1 and 28-886-2D)selected for thermobarometry.

Sample 15-017A shows remarkable similarity in both pressure and temperature using TWEEQU and WEBINVEQ 42). TWEEQU P-Tplot shows a tight intersection of 35 equilibria with 4 independent reactions flable 4-2) at 1400 bars and 4350C.

WEBINVEQ results in an ellipse with a center at 1770 bars and 4500C. The average electron microprobe analyses are given in Table 4-3.

Table 4-2. A set of four independent reactions applied to the assemblage Grt + Bt + Chl + PI + And + St + Qtz in altered basaltic rocks from the Campbell-Red Lake Mine Complex (CRLMC).

Fe-Mg exchange -tion (thermom~ter): (1) almandhe + phlogopite = pppe+ annite Net transfer reaction (barometer) (2) 2 andalusite + quartz + grossular = 3 anorthite (GASP barometer) Other reactions (3) 4 Quartz + 3 Chlorite + 2 Andalusite = 5 Pyrope + 12 Hz0 (4) 25 Quartz + 6 Staurolite = 46 Andalusite + 8 Almandine + 12 Hz0 Note: The other 31 doason the P-Tplots arc Encar combinations of the above dcms. Fig- 4-1. TWEEQU P-T plot illustrating the scatter of equilibria when Feehloritoid is used. A total of 93 merent reactions are plotted with 5 independent reactions. Mineral assemblage includes Grt + Bt + Chl + St + Cld + P1+ Qtz + And. Compare this figure to 4-3. Aluminosilicate polymorphs after Holdaway (197 1). Mineral abbreviations after Kktz (1983). Temperature ("C)

Figure 4-2. 'IWEEQU (Be- 1991) P-T plot for sample l5417A. Note the tight intersection of reactions around 1400 bus and 435°C. The ellipse represents the least-squ- P-Testimate using WEBINVEQ (Gdon 1992). The center of the ellipse is at 1760 bars and 450°C. Mine& include Grt + Bt + Chl + St + PI + Qtz + And. The bold vertical line is the Grt-Bt thermometer* AlOmitlosilicate polymorphs after Holdaway (1971). Mined abbreviations after Kretz (1983). Table 4-3. Average electron micropn,bc analyses of minerals in specimen 15-017A

Grt Bt Chl P1 St And Wg flm Core Rim Si02 37.72 37.63 36.49 2S.01 45.99 27-80 37.47 0.64 1.42

Structural Formulae Si 3.036 3.045 2721 u4) 0.000 0.000 1.280 1.988 2.008 0.417 Ti 0.004 0.005 0.079 Fe3+ 0.007 0.000 0.112 Fe2+ 1.616 1.794 0.864 Mg 0.269 0.265 1.353 Mn 0.890 0.732 0.011 Ca 0.221 0.180 0.012 Na 0.005 0.006 0.014 K 0.001 0.009 0.871 ct 0.03 0.004 0.04 Zn - - - 0 12.000 12.000 10.000 OH 0.000 0.000 2.000 The same assemblage as 15-017A occars in sample 28-8862D,approximately 800m deeper in the mine. TWEEQU displays a tight intersection of 35 equilibria with 4 independent mactiotls cable 4-2) at 2000 bars and 475% while WEBINVEQ dtedin an ellipse with a center at slightly lower pressure of 1760 bars and viaDslly identical temperatme of 47OOC (Figure 4-3). The average electloa microprobe analyses for 28- 886-2D am given in Table 44.

Sample 24-88-1contains the same mineralogy as 2413, but 24-88-1 shows fpr

better convergence of 35 equilibria with 4 independent reactions (Table 4-2) at 1700 bars and 4800C with TWEEQU (Figure 4-4). WEBINVEQ resulted in a tight ellipse with a center at a much lower presswe of 1030 bars with virtually the same temperatme of 480% The average electron microprobe analyses for 24-88-1 are given in Table 4-5. For the sake of clarity and the fact that the thermodynamic data for chloritoid are not well known it was omitted fiom the P-Tcalculations for sample 2413 and 24-88-1.

Sample 34L-236-1 is an altered felsic rock with a different mineral assemblage than the previous altered basaltic rocks. However, thennobarometry yields very similar ~sdts.TWEEQU shows an almost perfect intersection of 24 equilibria with 3 independent reactions gable 4-6) at 1800 bars and 48oOC (Figure 4-5). However, WEBINVEQ results in a large ellipse with a center at 1673 bars and 54S°C. The large error ellipse is attributed to the uncertainties in the thermodynamic database (TWQ 1.02) for cordierite in WEBINVEQ versus the updated sotution model for coderite (Berman and Aranovich 1996) used in TWEEQU. The average electron microprobe analyses for 34G236-1 are given in Table 4-7.

Although, samples 9521-1 and 2413 appear to be in textural equilibrium they both yield poor results. The 'WEEQU P-T plot for sample 9521-1 displays a large scatter of equilibtia and WEBINVEQ results in a nonsensical P-T estimate of 15150 bars and 515W with a very large ellipse. Therefore, thermodynamically not all minerals in the rock are in equilibrium. However, the temperature (510°C) concurs with other Temperature (OC)

Figure 4-3. 'IWEEQU mennan 1991) P-T plot for sample 28-886-W. Note the tight intersection of reactions around 2000 bus and 47S°C. The eIlipse represents the least-sqparrs P-Testimate using WEBINVEQ (Gordon 1992). 'Ibe center of the ellipse is at 1758 bars and 472OC. Mine& include Grt + Bt + Chl + St + P1+ Qa + And. The bold vertical line is the Grt-Bt thennometer. Alumhsilicate polymorphs after Holdaway (197 1). Mineral abbreviations after Kretz (1983). Table 4-4. Average electron micropn,be analyses of minerals in specimen 28-886-2D.

Grt Bt Chl P1 And St Mt Core Rim Si02 37.49 37.41 36.95 25.77 45.13 36.01 28.90 0.78

Structural fordae: Si 2.975 W4) 0.000 M(6) 1.985 Ti 0.005 Fe3c 0.003 Fe2+ 1.702 Mg 0.324 Mn 0.772 Ca 0.204 Na 0.003 K 0.002 Cr 0.004 Zn - 0 12.000 OH 0.000 XCO, = 0.7 -0 = 0.3 Grt Model = Bemum and Atanovich (19%) Bt Model = Berman and Aranovich (19%) PI Model = Fuhrman and Lindsley (1988) 4 hdepcndent Reactions

Temperature ("C)

Figure 44. TWEEQU (Berman 1991) P-Tplot for sample 24-88-1. Note the tight intersection of reactions atoand 1700 bas and 480°C. l%eellipse mptesents the least-squares P-T estimate using WEBINVEQ (Gordon 1992). The center of the ellipse is at 1033 bars and 479.C. Minerals iaclude Gn + Bt + Chl + St + Pl + Qtz + And. The bold vertical lint is the Grt-Bt thermometer. Aluminosilicate polymorphs after Holdaway (197 1). Mineral abbreviations afkktz (1983). Table 4-5. Average electton mictoptobe analyses of minetals in specjmen 24-88-1.

Care Rim SiO2 37.83 37.64 35.56 24.71 46.34 25.24 27.89 0.98 Figure 4-5. TWEEQU (Bemun 1991) P-Tplot for sample 34L-2361. Note the tight intersection of ceactions around 1700 bars and 470°C. Least-squam P-Testimate using WEBINVEQ (Gordon 1992) rrsulted in a P-Testimate of 1700 bars and 540°C with a large error ellipse due to the fewer narnbcr of phases in the reactions. Miaetals indude Crd + Bt + Chl + St + P1+ Qtz + Mg + Ms. Aluminasfic8te polymotphs after Holdaway (1971). Mined abbreviations after KRtz (1983). Pl Crd Bt Ms Mig St Cht Elm Core Rim . Si02 50.31 46.86 49.35 37.17 47.62 34.23 27.71 26.13 0.53 A1203 Ti02 Fe203 Feo MgO MnO cao Na20 DO Zno Cr203 H20 Table 4-6. A set of three independent reactions applied to the assemblage Crd + P1+ St + Bt + Cbl + W + Mrg + And + Qtz in altered felsic rocks from the Campbell-Red Lake Mine Complex (CRLMC).

(1) 19 Quartz + 8 Margarite + 2 Chlorite = 8 Anorthite + 5 Cordierite + 16 Hz0

(3) 45 Quartz + 62 Mergadte + 8 Annie = 62 Anorthite + 8 Muscovite + 6 Stamlite + 50 Hz0 Note Tbe other 21 donsas tht POTplot art liiamhhatiolls of the above reactions. samples in the mine and with the temperature (4750C) determined using the Grt-Bt thermometer on the same sample (Figtm 4-6). The TWEEQU P-T plot for sample 2413 also shows a wide scatter of 35 equilibria with 4 independent reactions flable 4-2).

Plagioclase in this rock has a highly variable composition (MO-An87) between grains indicative of disequilibrium. However, WEBINVEQ yields a relatively small ellipse with results that are very similar to other P-T estimates in the Red Lake Mine (Figure 4- 7). Furthermore, the temperature from Grt - Bt thermometer calculated with 'IWEEQU overlaps with the temperature estimate of WEBINVEQ. Refa to Table 4-8 and 4-9 for the average electron micr0p~)beanalyses for samples 9521-1 and 2413, respectively. The diffennces in P-T estimates between TWEEQU and WEBINVEQ can best be explained by the use of different activity models for garnet (J'able 1) and the lack of an activity model for cordierite in WEBINVEQ. The absence of fluid activity models in WEBINVEQ must only have a minor effect on the P-Tesimates because samples 15- 017A and 28-886-2Dare in good agreement with TWEEQU. Results fmn detailed petropphic analysis and incorporated mined chemistry (see Chapter 3) yield significantly different P-T estimates compared to previous studies in the CRLMC (Mathieson 1982, Mathieson and Hodgson 1984 and Christie 1986). Although previous temperature estimates PIP very similar, pressure is much lower. Temperature ("C) Figare 4-6. Grt - Bt thermometer for sample 9521-1. The temperature comsponds to about 479C at 2000 bars. The Grt-Bt thennometer is based on the exchange between Fe-Mg (Few and Spear 1978). Temperatrue was calculated using TWEEQU (Beman 1991) with the Grt and Bt models of Beman and Aranovich (1996), respectively. Note that although the assemblage Grt + Bt + Chl + Hbl(Fe-Ts) + P1+ Zlm + Ank is not in equilibriam the calculated temperature is similnr to the other samples. Aluminosilicate polymorphs after Holdaway (1971). Nineral species abbreviations after Krea (1983).

Table 4-8. Average electron daqmbe analyses of mbdsin specha9521-1.

Grt Bt Cbl PI Hbl Ilm A& Cart Rim Si02 37.08 37.10 34.32 23.51 60.98 40.00 0.65 0.27 Table 4-9. Average electron mictoprobe analyses of minerals in spechen 2413.

Grt Bt CbL P1 CId St llrn Core Rim Si02 36.86 3684 34.30 23.36 50.73 24.22 27.92 3.23

Stroctaral formulae: Si 3.011 3.012 w4) 0.003 0.001 N6) 1.977 1.974 Ti 0.003 0.006 Fe3t 0.018 0.013 Fe2+ 2.170 2273 Mg 0.188 0.164 Mn 0.390 0.336 Ca 0.251 0.225 Na 0.002 0,002 K 0.002 0.062 cr 0.002 0.005 Zn - - 0 12.000 12.000 OH 0.000 0.000 Calculated values of ptespte and temperature vary between 1000-2200 ban and 435- SSOOC (Figure 4-8). Exclading samples 9521-1,2413 and 24-88-1, which show evidence ofdiseqtlilibrium, and Psing only the samples which were consistent between TWEEQU and WEBINVEQ, the P-T conditions can be narrowed down even farther to between 1400-2000 bars and 435-55m Emw are conservatively estimated to be ~200bars and &20% Previous P-T estimates derived fmm petrogenetic grids and atsenopyrite thermometry vary from 34kbars and 440-510% (Christie 1986) at the Campbell Mine and 3.842 kbars and 520-540°C (Mathieson 1982) at the Red Lake Mine (Figure 4-9). These studies fail to take into account the actual mineral chemistry of the silicate phases

and rely solely on petmgenetic grids to constrain the P-T of the altered rocks within the CRLMC* A more rigorous petrogenetic grid for metapelites was developed by Spear and Cheney (1989). The P-T results for all samples are plotted on this P-T grid (Figure 4-

10). It is clear from the P-T dtsdiscussed above that neither P-Tgrid is applicable to the alted rocks in the CRLMC. This is most likely due the high Mn and Zn content of garnet and staurolite, respectively. The effect of adding these two elements is to expand the P-T stability fields of the two minerals and to cause the P-T equilibrium curves to broaden into "zones"of finite width. For instance, it has been recently demonstrated that 0.1-0-4 wt.8 bu.rock kfh lowers the temperature at which the garnet& isograd first appears by 1- (Mahar et al. 1997). Zaleski et aL (1991) have shown that although their parageneses are supemcially similar, the P-T grids used for pelitic bulk-rock compositions are not appropriate for altered rocks. This is especially true for rocks in the CRLMC that have undergone significant premetamorphic hydrothermal alteration resulting in abundant hydmthemal biotite and chlorite as well as clay minerals that have subsequently fodaluminous minerals (Le. chloritoid, andahsite, staurolite, garnet cordierite and dumortierite) at the Red LAce Mine. The metamorphism of the alteration assemblages will only result in nmystalli;ration of the biotite and chlorite (Stanton

Temperature CC) Figure 4-9. Schematic P-T phase diagram for part of the "ideal" pel& system N%O - KO - FeO - MgO - &03 - SiO, - KO relevant to the metamorphism of pelitic rocks. Reactions not involving muscovite an dashed. Reactions involving chiotitoid are not showa. Note that all assembhges include phgioclase. Shaded erras am the metamorphic conditions deduced by Mathieson (1982), Christie (1986) and this study. Bathomnes (Carmichael 1978) are displayed as dashed horizontal lines. Note that the stable assemblage Grt-Bt-And constrains the rocks to B2 or B1. Results fraa TWEEQU (Berman 1991) and WEBINVEQ (Gordon 1992). Also no& that results fmm thennobarometry do not match with the P-T grid. Mineral abb~viationsaf&r Kretz (1983). Temperature ("C) Figure 4-10. Petrogenetic grid for the system KUTFe0-MgO-Al203Si02-H20 adopted from Spear and Cheney (1989). The P-Trrsults using TWEEQU ('em 1991) and WEBINVEQ (Gordon 1992) axe plotted as circles. The arrows point to where the bolded univariant curves that the racks plot on. This pettogenetic grid is very unreliable for the rocks in the Campbell-Red Lake Mine Complex. Compare with the petrogenetic grid of Cannichael et al. (1987). 1989) and re-equilibration of the duminous phases (ie. clay minerals) to form new alomiflous minerals, like chiodtoid and statuolite, depending on the metamorphic grade.

4.4 T-X* Conditions Results from TWEEQU in the Red Lake Mine indicate that the partial pressure of Hz0 (-0) in the Red L,ake Mine was quite Low. It is reasonable to assume that the only other fluid phase involved in metatnorphism is C% Therefore, if PE20 is low then must k high. The composition of the fluid phase can have dramatic effects on the P-T estimate using 'IWEEQU. This is best illustrated by Figure 4-11. 1is clear from this figure that with higher the naction eqoilibria get displaced to higher P-T conditions. The Grt - Bt exchange thermometer acts as a reference line because it is independent of the fluid phese and is therefore, not affected by varying fluid compositions. The H2O-C9 ratios were iteratively adjusted until the reaction equilibria overlapped with the Grt - Bt thermometer and also converged upon themselves to give the best intersection of all equilibria. It is evident from Figure 4-11 that the "best fit" occurs at a very high XC% of 0.7 in sample 28-8862D. This procedure was repeated for all samples that were subjected to thennobarometry using TWEEQU. Complete P-T- XC% conditions detezmined with TWEEQU arr listed in Table 4-10. Samples 15-017A, 24-88-1 and 28-886-2D are altered basaltic rocks and yield essentially the same results. Sample 34L-236-1 is an altered rhyolite with basically the same P-T as the altered basaltic cocks, but with notably lower PC% (0.45). The results show that the XC% vary between 0.45 and 0.85. The XC% conditions also show a progressive increase with depth. The high Xc% conditions have a number of significant effects on the observed mineralogy of the rocks in the CRLMC. High XC% conditions will stabilize Cwbearing assemblages relative to their decarbonated products. Evidence for very high XC% conditions of metamorphism are indicated by the preservation of the banded quartz-ankerite (dolomite) Temperature (OC)

Figure 4-1 1. Sequence of TWEEQU P-T plots for sample 28-8 86-2D to illustrate the dramatic effitthe activity of the fluid phase has on the intersection of the equilibrium curves. The Grt-Bt exchange thermometer (bold line) is 6ted because it is independent of the fluid phase. The equilibrium curves are displaced to higher temperatores with increasing water activity. The best intersection occurs where the equilibria converge and overlap with the Grt-Bt thermometer at XC4of0.7. Note that the P-Tscale for every diagram is the same as the lower left Table 4-10. Summary of P-T-X- conditions in the Red Lake Mine with TWEEQU. Sample Pnsarrt Temperature XC&

15417A 1400 bars 435W 0.85 24-88-1 1700 bats 480% 0.70 28-886-23) 2000 bats 475W 0.70 34L-236-1 1800 bars 48OOC 0.45

veins (Figure 4-12). Some banded quartz-ankerite veins display evidence of metamorphic reactions. Hornblende is commonly only developed in quartz-carbonate veins and rocks rich in ankerite. In sample 15-017B hornblende is developed in a quartz- carbonate cockade breccia. Highly altered wall-rock fragments are enveloped by successive layers of quartz and bladed ankerite. The hornblende apparently grew during metamorphism and clearly cross-cuts the fabric of the cockade breccia The XC~Z conditions of metamorphism are significantly higher than the previous estimates by Christie (1986) from the Campbell Mine. Christie (ibid) used the assemblage Ma + And + Qtz + Cld + Ms + Do1 with "ideal"activities and an inferred pressure of 34kbars to arrive to arrive at T-XC% conditions between 440-SLOW and 0.3-0.55 (Figare 4-13) in an ideal binary system of pure C% and Hz0 with the assumption of ideal mixing among C% - Hz0 fluid and ideal activities of the silicate phases. Results indicate that Christie's pressure estimate is too high. Although, the assumption of ideal mixing has been shown to be an inappropriate (&errick and Jacobs 1981), it has only minor effect on the temperature estimate. The non-ideal mixing model of Kerrick and Jacobs (1981) for CO;? - Hz0 fluid was used in all calculations with TWEEQU in this study. Mole fraction C4 Figure 4-12. Temperatun-Mole fraction CO, diagram which demonstrates the effects of p~ssuxeand mole fraction COz on the reaction 3 Cc + Tr + 7 C02= 8 Qtz + 5 Do1 + KO. Note how the stability field for Qtz + Dol is expanded with increasing press- and mole fraction COP The pressure for each mction in bars is highlighted. The shaded area beneath 2000 bars illustrates the conditions under which the banded quartz4olomite veins will remain stable. Mineral abbreviations PRer Kcea (1983). 4x2

900- mu

506 -

P = 4 kbar 100 - Assemblage includes qtz

I 1 I L m

Fig. 4-13. T-X, diagrams for selected stable reactions in the system CaO - MgO - 40, - SiO, - KO - C4- KO at 3 and 4 kbar. The reactions were calculated using the themochemical data of Helgeson et aL (1978) and the APL computer programs written by D. M. Carmichael. ModSed from Christie (1986). UDtscussion The conditions of metamorphism h the CRLMC can be well established using the themobammesic methods of TWEEQU aad WEBINVEQ on the low-variant assemblages. The wnditions of metamorphism in the Red Lake Mine vary between 1.4- 2.0 kbam and 435-SSWC with Xqconditions ranging between 0.45 and 0.85. Both pressure and ternperatore apparently inawse with depth while XC% deaeases with depth. The high Xqconditions of metamorphism have dramatic effixts on the convergence of equilibria The higher Xqconditions du~gmetamorphism depress the equilibria to lower pressures and temperatures. The staurolite-in and the chloritoid- out isograds am most likely dated to the increase in temperature with depth. The separation of the isograds is appmximate1y 750 meters. PDTresults indicate a very high geothermal gradient of about 7&900Cflan. The high geothermal gradient is consistent with contact metamotphism by a nearby heat some at depths of 6-7 lan assuming 1000 bars is equivalent to about 3.5 km. By taking into accomt the geothermal gradient, the

temperature change from the stamlite-in isograd to the chloritoid-out isograd is approximately 50-70Oc which corresponds with the estimated temperature difference between samples 15-017A and 34L-236-1. The Campbell-Red Lake Mine Complex is a metamorphosed Arcbean gold deposit. The age of mineralization can be tightly constrained between 2718 kl (Cobu and Wallace 1986) 2714 il Ma (Corfb and Andrews 1987) by both preore and post-ore intrusions, the Dome stock and cross-cutting QFP dykes in the Red Lake Mine, respectively. Contact metamorphism was coincident with the infrusion of the marginal phase of the Trout Lake batholith (Le. the Wslsh Lake ploton) at 2699 k11M4 (Noble ct aL 1989) and was overprinted by low-grade regional metamorphism dhgthe Kenoran orogeny at 2650 Ma (Yo& et aL 1991). Intense pre-metamorphic hydrothermal alteration has affected nearly all of the rocks in the CRLMC. Hydrothermal alteration was so intense that the bolk-composition of the original basaltic rocks now plots entirely witbin the field of pelitic rocks. Subsequent metamorphism has resulted in the rich variety of low-variance mineral assemblages. The maximum-phase assemblages include:

Grt+Bt+Cbl+St+Cld+And+Pl+Qtz+Ilm+Ank+Tur k Cum The low-variance assemblages could have only arisen by the metamorphism of high- variance assemblages. Metamorphism occorred in a rockdominated system with only minor quantities of fluid. The otiginal duminous alteration would have taken place in a fluiddominated system which typically give rise to high-variance assemblages commonly consisting of only one or two minerals in each zone. In the general case, where both the original small sample of rock and vast quantity of fluid have arbitnuy composition, only one mineral is stable. The zoning of mineral assemblages enveloping the ''Main Zone" at the Red Lake Mine is Metred to represent zoned hydrothermal alteration patterns associated with gold mineralization. The "Main Zone" is enveloped by three mineralogically distinct maximum-phase mineral assemblages: (l)Chl+Pl+Grt+And+Qtz+St+Cld+Bt+ILmf Cum(Distal) (2) Hbl + Bt + Chl + PI + Qa + A& + Mt + Ilm f Ath (Intermediate) (3) Bt+Ank+Qtz+Ms+Pl+Mtf Chl (Proximal) The zoning of mineral assemblages ammd the '%hhZone" at the Red Lake Mine is inferred to represent metamorphism of hydrothermal alteration. The outer zone, dominated by low-variance aluminous assembhges, is inferred to have formed hma pmtolith rich in kaolinite (Lega zone of advanced iugillic alteration). Local domains ("bleaching") within this zone are composed almost entirely of andalusite, muscovite, quartz and ilrnenite. The intermediate zone, dominated by amphiboles and chlorite, may have formed from a chlorite-rich pmtolith (i.e. a zone of intermediate argillic alteration). Close to the ore-beating structure, the proximal zone is inferred to have formed from a protolith rich in biotite, muscovite, quartz and anlcedte (Lega zone of porsssic alteration). During metamorphism, hydrothermal biotite, muscovite, chlorite, quartz and &rite are inferred to have recrystaked and re-equilibrated with newly formed minerals such as garnet, staurolite and chloritoid, while the lower temperature hydrothermal clay minerals in the outer zone were completely replaced by the newly fonned minerals. The mineral assemblages demonstrate that the whole Red Lake Mine is in amphibolite facies rocks. Rock collected from near surface contain the assemblage Grt + Hbl + P1 (An29) + Bt + Cbl + Qb. The stawolite-in isograd occurs at least 500 meters below the hornblende-oligoclase isograd Therefom, the statuolite-in isograd does not represent the transition from greenschist to amphibolite facies. The mineral assemblages pre~e~edin the CRLMC demonstrate that the transition fiom greenschist to arnphibolite facie assemblages in weakly altered basaltic rocks occurs before the transition of greenschist to arnphibolite facies assemblages in highly altered basaltic rocks (essentially pelites) with aluminous assemblages. Therefore, the Red Lake Mine is not transected by a greenschist/mphibolite facies transition as suggested by Andrews and Hugon (1985) and Andrews et aI. (1986). hstead, the staurolitein isograd strikes roughly NZWE and musects the Red Lake Mine underground at about the 15th level. The one constraining sample on stuf'ace is 2.5 km east of tbe Red Lake Mine. This requires that the dip of the isograd to be 30° to N600W. Two isograds have been mapped in the Red Lake Mine. Staurolite-in and chloritoid-out isograds strike approximately N2CPE and dip 3- compared to the mint stratigraphy which st&es approximately N45W and dips between 40-750W. Therefore, it is clear that the isogeds ctoss-cut the dominant structural "grain" and the set of alteration zones that surround the ore at the CRLMC and metamorphism is not only post-kinematic, but also post-alteration and post-ore. The low-variance assemblages pennit accnrate P-T estimation. Two methods of thennobarometric analysis were ariliz#l, TWEEQU and WEBINVEQ, and they yield similar results. P-T conditions are very well constrained between 1400-2000 bars and 435-48WCwith TWEEQU and 1000-2200 bars and 450-550% with WEBINVEQ. The isograds are most probably dated to the increase in temperature with depth in the mine since the vertical scale of sampling was approximately 1700 meters (5700 ft) which corresponds to only 500 bars. Samples that display thermodynamic disequilibrium were not used. The differences in P-Tresults are mainly attributed to differing activity- composition models between the two programs. P-T results indicate a very high geothermal gradient of about 70-9OWkm. 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The following tables list the minerals recorded in samples collected from the Red Lake Mine with brief notes. The samples ere listed in orda from the s&i to the 38h level of the mine. The drillhole intersection through the ''Main Zone" on the 34th level Iists the ssmples sequentially from the footwall to the hangingwall. The nomenclature of the samples is quite complex. Samples from the surface have letter designations at the beginning of each sample (i-e.S-1 and BR-1). Samples hwn surface diamond drillholes @DH) have the designation GC-95-21-1, which stands for the company name (Goldcorp), year the hole was drilled (95), the hole number (21) and finally the sample number (1). Samples from underground ddUholes normally start with the level from which the hole was drilled, followed by the hole number and finally the sample number (e.g. 34L-144-25). The footage of the sample number is listed in the following tables. All other sample numbers refer to specific grid kocations that are used in the mine. All sample numbers start with the level from which they were colIected, followed by a series of numbers which refer to locations on the mine grid. For example, sample 17-2347 was collected on the 17th level from the 2347 west drive.

Appendix B: Electron Microprobe Analyses

The following tables list the electron microprobe analyses before they were compiled for use in thennobarometry and also list any microprobe analyses not used. In all cases the primary standard (S-204) was dysed5 times for 300 seconds each time and the results were averaged. If any element deviated by & 0.2 weight percent the reset factors were manually adjusted. Standards we= coatin~allychecked throughout the pobe session, typically every 10-15 analyses, to check if the beam drift had affected the results. A thorough discussion of precision and accuracy can be fmdin inlair (1982) and Pen& (1946). Minerals selected for electron microprobe analyses were fmn three separate domains on each thin section. AU1 minerals in each domain were analysed three times in the core and three times in the rim to check for zoning. If no appreciable zoning was detected the analyses were then grouped and averaged from all three domains. These averaged or representative analyses were then used in the themobaromeeic calculations. Table B 1. Mir;roprube analyses of garnet from 9521-1.

Garnet I Garnet 2 Garnet 3 Average Cote Rim Core Rim Cw Rim Core Rim- Si02 37.21 37.24 37.16 37-13 36.86 36.94 37.08 37.10 A1203 Ti02 Fe203 Feo MgO Milo cao Na20 no Cr203

Alm 0.654 PrP 0.026 SPS Oil59 Grs 0,142 A& 0.023- Uva 0.001 0.004 0.04 0.W 0.012 0.000 0.007 0.003 Table BZ Microprobe analyses ofbiotite fiom 9521-1.

Biotite L Biotite 2 Biotite 3 Average Core Rim Core Rim Core Rim Core liim SiO2 34.48 34.64 34.20 34.18 34.18 A1203 Ti02 Fe203 Feo moMgO cao Nd0 no Cr203 H20

Structural formulae: Si 2.714 AK4) 1.286 Aim 0.334 0.117 Fe3+ 0.117 Fe2+ 1.51 1 Mg 0.730 Mn 0.013 ca 0.015 Na 0.037 K 0.888 Cr 0.000 0 10.000 OH sow -B3. -B3. analyses off

Cblorite 1 Cblontc 2 chlotid 3 Average- Core Rim Core Rim Core Rim Core Rirn Si02 23.22 23.29 23-83 23.57 23.41 23.76 23.49 23.54

StructPral form*: Si 2.617 2.615 Ax41 1.383 1.385 Al(6) 1.370 1.355 Ti 0.000 0.000 Fe3t 0.014 0.03 1 Fe2+ 3.179 3.131 Mg 1.350 1.367 Mn 0.031 0.047 Ca 0.056 0.070 Na 0.000 0.000 K 0.000 0.000 Cr 0.000 0.000 0 10.000 10.ooO OH 4.000 4.000 Table B4. Mictop~obeadyses of phgiocbfirrm 9521-1. Plagioclasc Plapioclase Piagioclase Average Care Rim Core Rim Core Rim Coze Rim Si02 6254 61.57 61.55 60.63 59.21 60-40 61.10 60.87 A1203 23.14 Ti02 0.00 Fe203 0.40 FeO 0,OO Mgo 0.06 Mu0 0.04 CaO 5.08 NaZO 8.56 K20 0.05 Cr203 -0.04 99.91

Smctural form* Si 2.774 a41 1.210 AW) 0.000 r1 0.000 Fe3+ 0.013 Fe2+ . 0.000 Mg 0.004 *. 0.002 Ca 0.241 Na 0.736 K 0.003 Cr 0.001 0 8.000 Table B5a. Mictopmbc analyses of amphibole fkm 9521-1.

A1203 r102 Fe203 FeO wo MnO cao Na20 Iao C1203 H20

Structural fomr;llae= Si - 6.13 1 N4) 1.869 AK6) 1.060 Ti 0.060 Fe3+ 0.509

Fez+ : 2.630 Mg 0.851 Mn 0.065 Ca 1.699 Na 0.382 K 0.053 Ct 0.000 0 22.000 OH 2.000 Structural formulae: Si 6.200 6.085 M4) 1.800 1.915 Jw6) 1.303 1.309 Ti 0.000 0.024 Fe3+ 0.210 0.239 Fe2+ . 2760 2.865 Mg 0.787 0.619 M. 0.066 0.051 Ca 1.799 1.827 Na 0.394 0.381 K 0.045 ' 0.067 Cr 0.000 0.000 0 22.000 22.000 OH 2.000 2.000 -.- 13 14 15 16 17 18 Average Si02 39.82 38.02 40.65 39.42 40.08 36.00 A1203 Ti02 Fe203 Feo MgO Mno Cao NU0 no cm3 H20 TableBda Microptobe analyses of ilmenite fkom 9521-1.

A1203 Ti02 Fe203 FeO MgO MnO cao Na20 no Cr203 TabkB6b. Uimptobe analyses of ilmcnite from 9521-1.

7 8 9 10 I1 Average Si02 0.52 0.94 0.60 0.56 0.60 A1203 Ti02 Fe203 Feo MgO MnO cao Na20 K20 Cr203 Table B7. Mimprobe analyses of anknite fmm 9521-1.

I 2 3 4 5 Average Si02 0.24 0.35 0.27 0.21 0.26 0.27 Table B8. Mic~op~obeanalyses of garnet from 15-017A.

Garnet 1 Garnet 2 Gmet 3 Average- Core Rim Core Rim Core Rim Cote Rim Si02 37.61 37.72 37.65 37.65 37.89 37.53 37.72 37.63 A1203 Ti02 Fe203 Feo MgO Mno cao Na20 Iao Cr203

Uva 0.000 <0.000 0.004 0.005 0.008 0.012 - 0.004 0.006 Table B9. Microprobe analyses of biotite ELom 15417A.

Biotite 1 Biotite 2 Biotite 3 Average

-03 Ti02 Fe203 Feo MgO Milo Cao Na20 no CR03 H20

Stractu formulae: Table B 10. Microptobe analyses of chlorite fiom 15417A.

Chlorite 1 Chlorite 2 Cbloritt 3 Average Core Rim Core Rim Cote Rim Core Rim Si02 24.88 24.73 25.23 24.86 24.90 25.46 25.00 Z.02 A1203 Ti02 Fe203 FeO MgO Mil0 cao Na20 K20 Cr203 H.20 Table B 11, Microptobe analyses ofphgidclase hn15-017A.

COG Rim Core Rim Core Rim Cote Rim Si02 46.02 46.50 45.91 45.88 45.80 45.85 45.91 46.08 A1203 Ti02 Fez03 Feo MgO MnO cao Na20 no Ct203

Structural folmalae= Si 2.106 2.128 AK4) 1.855 1.835 AW) . 0.000 0.000

Ti 0.001 * 0.000 Fe3t 0.000 0.000 Fe2+ .' 0.020 0.023 Mg 0.004 0.003 Mn 0.000 0.000 Ca 0.922 0.897 Na 0.102 0.123 K 0.001 0.006 Cr 0.003 0.002 0 8.000 8.000 Table BIZ Microprobe analyses of stamlite fbm l5Ql7A with ZnO,

StamIite 1 Staurolite 2 Average- Core Rim Core Rim Core Rim Si02 27.85 27.74 27.81 27.80 27.83 27.n A1203 Ti02 Fe203 Feo MgO Mno Cao Na20 K20 Zno En0

Table B14. Microprobe analyses of magnetite fkom 15417k Uagnetite 1 2 3 4 5 6 Average SO2 0.66 0.60 0.51 0.78 0.64 0.67 0.64 A1203 Ti02 Fe203 Feo MI@ MnO Cao Na20 no CR03

Structural fomuk Si 0.025 0.023 Al(4) 0.000 0.000 A461 0.056 0,050 Ti 0.004 0.000 Fe3+ 1.878 1.898 Fe2+- 1.007 0.998 Mg 0.016 0.011 Mn 0.000 0.000 Ca 0.007 0.015 Na 0.000 0.000 K 0.000 0.000 Cr 0.007 0.005 0 4.000 4.000 Structural fon Si Om( AK4) O.( AY6) 0.t Ti 0.1 Fe3+ 0.1 Fez+ 0.1 Mg 0.i Mn O.( Ca Om( Na Om( K 0.t Cr Om( 0 3 .I Table 816. Microprobe analyses of garnet hm24-88-1. Garnet 1 Garnet 2 Garnet 3 Average- Core Rim Core Rim Care Rim Core Rim Si02 37.78 37.57 38.26 37.71 37.46 37.65 37.83 37-64 A1203 Ti02 Fe203 FeO mo Mil0 cao Na20 K20 0203

Stntctwd formulae: Si 3.023 3.011 Al(4) 0.000 0.000 Al(6) 1.954 1.986 Ti 0.003 0.000 Fe3t 0.035 0.011 Fe2+ 1.816 2382 MS 0.191 0.191 Mn 0.710 0.259 Ca 0.286 0.167 Na 0.000 0.000 K 0.000 0.000 Ct 0.005 0.003 0 12.000 12.000

Alm 0.605 0.794 0.640 0.795 0.645 0.799 0.630 0.7% Ow 0.064 0.064 0.074 0.065 0.068 0.062 0.068 0.064 , SP 0.236 '0.086 0.209 0.087 0.206 0.082 0.217 0.085 Grs 0.075 0.046 0.049 -0.035 0.050 0.039 0.057 0.040 A& 0.018 0.006 0.020 0.02 0.021 0.018 0.019 0.009 Uva 0.003 0.04 0.008 0.016 0.011 0.000 0.008 0.007 -- Table B 17. Microprobe analyses ofbiotite from 24-884. Biotite 1 Biotite 2 Biotite 3 Averam- Core Rim Cozc Rim Core Rim Core Rim SO2 36.25 35.61 35.24 34.73 35.42 36.10 35-64 35.48 Al203 Ti02 Fe203 Feo MgO MnO Cao Na20 KZO Cr203 mo

Structural formulae: Si 2.708 2.666 fw4) 1.292 1.334 Al(6) 0.399 0.370 TI 0.078 0.073 Fe3+ . 0.138 0.141 Fe2+ 1.240 1.273 Mg 0.961 0.991 Mn 0.005 0.006 Ca 0.014 0.019 Na 0.013 0.000 K 0.907 0.926 Cr 0.002 0.000 0 10.000 10.000 OH 2.000 2.000 \ Table B 1%.Microprobe dysgof chlorite ftom 24-88-1.

Chlorite 1 Chlorite 2 Chlorite 3 Average Core Rim Core Rim Core Rim Core Rim Si02 24.43 25.33 24-03 24.85 24.18 25.42 24.21 25.20 AD03 Ti02 Fa03 FeO MgO Mno cao Na20 Fa0 0203 H20

Structural formulae: Table 819. Microprobe analyses of plagioclase from 24.884.

Plagioclase 1 Plagioclase 2 Plagioclase 3 Average- C& Rim con Rim 6 Rim Cole Rim Si02 44.88 46.62 45.86 46.78 45.84 48.04 45.53 47.15 A1203 Ti02 Fe203 FeO MgO Mi0 Cao Na20 no Cr203 Table B20. Micfoprobe analyses of chloritoid fiom 24-88-1.

Chidtoid Chloritoid2 Chloritoid3 Average Cort Rim Core Rim Core Rim Coct kim Si02 24.52 2577 24.76 24.92 25.70 25.76 24.99 25.4% A1203 Ti02 Fe203 FeO MgO Ma0 cao Na20 K20 Cr203 H20 Table B21. Microprobe anaLyses of staptolite from 24-884 with ZnO,

- Cone Rim Con Rim Core Rim Cm Rim Si02 27.53 29.21 27.38 27-73 27.49 28-01 27.47 28.32 A1203 Ti02 Fe203 Feo wo MnO cao Na20 K20 Zno En0 Table B22. Microprobe analyses of ilmenite fkm 24-88-1.

1 2 3 4 5 6 - 7 Average Si02 1.13 0.99 0.91 0.73 0.79 1.54 0.76 0.98 Al.203 Ti02 Fe203 FeO MgO MnO cao . Na20 K20 Cr203

Structural Formulae: Si AK4) N6) Ti Fe3+ Fe2+ Ms Mil Ca Na R Cr 0 -2 Ganrtt4 Core Rim Cort Rim CCKC Rim Core Rim cbm Rim Si02 36.73 36.79 36.59 36.81 36.99 36.76 37-12 36.99 36.86 36.84 20.54 20.67 20.65 20.46 0.04 0.20 0.04 0.09 0.22 0.0s 0-13 0.00 32.96 34.40 32.94 33.64 1.57 1.22 1.60 1.28 4.98 4.67 5.20 4.73 2.33 2.02 2.38 2.16 0.00 0.04 0.06 0.00 0.00 0.04 0.04 0.00 0.04 0.12 0.09 0.11 TabIe B24. Microprobe analyses of biotite fhm 24f3,

Biotite 1 Biotite 2 Biotite 3 Average Core Rim Core Rim Core Rim Core & Si02 34.27 33.73 34.48 34.35 34-44 34.50 34.M 34.19 Tabb B25. Microptobe analyses of chlorite fkmn 2413.

Chlorite 1 Chlorite 2 Cblotite 3 Average Core Rim Coe Rim Core Rim Car+ &m Si02 23.52 23.41 23.44 23-18 23.17 23.44 23.38 23.34

Structural formulae: Si 2.588 2.592

Al(4) , 1.412 1.408 Ai(6) 1.507 1.485 Ti 0.000 0.007 Fe3+ 0.000 0.000 Fe2+ 2.654 2.647 MS 1.770 1.787 Mn 0.004 0.009 Ca 0.004 0.002 Na 0.000 0.OOO K 0.011 0.010 Cr 0.006 0.007 0 10.000 10.000 OH 8.OOO ,8.000 Table B26. Microprobe analyses of plagioclase hm2413. Average 7 Core Rim Core Rim Core Rim Corn Rim Si02 48.24 46.87 48.29 54.23 54.68 5206 50.40 51.05 A1203 Ti02 Fe203 Feo MsO Mil0 cao Na20 En0 Cr203 Table B27. Microptobe analyses ofchloritoid fiom 2413.

Ctdoritoid 1 Chloritoid 2 Chloritoid 3 Average Com Rim Core Rim . Core Rim Core Rim Si02 24.24 24.43 24.39 23.91 24.27 24.07 2430 24.14 AI203 Ti02 Fe203 FeO MgO Milo cao Na20 no Cr203 H20

Structaral formulae: Si 2.069 2.073 Al(4) 0.000 0.000 Al(6) 3.878 3.886 Ti 0.000 0.000 Fe3+ . 0.000 0.000 Fe2+ 1.729 1.713 Mg 0.253 0.253 Mn 0.043 0.040 Ca 0.005 0.02 Na 0.000 0.005 K 0.002 0.008 Cr 0.009 0.008 0 10.000 10.000 OH 4.m -.4.000 Table B28. Microprobe analyses of statmite fbm2413 with ZaO,

Average Coe Rim Core Rim axe Rim Cote Rim 27.73 27.88 28.16 27.74 27.82 28.17 27.90 27.93

Structural fomh Table B29. Microprobe anaLyses of ilmenite from 2413.

1 2 3 4 5 6 Average Si02 0.69 0-64 6-77 6.70 1.58 3.02 3.23 A1203 m2 Fe203 Feo MgO MnO Cao Na20 no Cr203 Table B30. Microptobe analyses of garnet fkom 26-917A

Garnet 1 Garnet 2 Garnet 3 Avenge Core Rim Core Rim Car Rim Core & Si02 37.13 37.75 36.96 37.21 36.59 37.07 36.89 37.34 ill203 20.74 Ti02 0.07 Fez203 0.52 Feo 26.68 MgO 0.92 MnO LO. I4 cao 4-84 Na20 0.02 no 0.01 cm3 -0.00 100.83

Structural formulae: Si - 2961 3.007 M(4) 0.000 0.000 AI(6) 1.971 1.898 Ti - 0.001 0.04 Fe3t 0.027 0.091 Fe2+, 1.781 1.837 MS 0.112 0.163 Mn 0.707 0.545 Ca 0.402 0.458 Na 0.000 0.000 K 0.000 0.000 Cr 0.000 0.003 0 12000 12.000

-. n 3 3 3 3 3 3 9 9 \ Alm 0.593 ' 0.612 0.613 0.611 0.581 0.598 0.596 0.60'7 prP 0.037 0.054 0.035 0.038 0.038 0.036 0.037 0.042 SPS 0.236 ,0.181 0.211 0.192 0.241 0.221 0.229 0.198 : Gts 0.1U) 0.103 0.130 0.137 0.117 0.112 0.123 0.118 A& 0.014 0.046 O.Ol2 - 0.023 0.022 0.025 0.016 0.031 Uva 0.000 -0.00Q 0.000 0.000 0.000 0.008 0.000 0.00Q Table B3 1. Microprobe analyses of amph'bo1e and t mite finnn 26-917A

ArnphiboIes Biotite 1 2 3 Average 1 2 Si02 52.83 5221 5222 5242 36.05 33.44 A1203 Ti02 Fe203 FeO MgO MnO cao Na20 K20 Cr203 H20 Table B32 Microptobe analyses ofph&ioclasefran 2641711 PlegiocIase 1 2 3 4 Average Si02 44.09 44.94

Structural formulae: Table B33. Microprobe analyses of garnet fiom 28-886-2D.

Ganrct 1 Garnet 2 Garact 3 Average Core Rim Core Rim Core Rim Core & Si02 37.60 37.50 37.34 37.34 37.53 37.38 37.49 37.41 A1203 Ti02 Fe203 Feo hago Mno cao Na20 K20 Cr203

Ah 0.554' 0.574 0.568 0.588 0.579 0.640 0.567 0.601 pr~ 0.109 0.113 0.113 0.112 0.101 0.092 0.108 0.106 SP 0.274 - 0.251 0252 0.239 0.245 0.208 0.257 0.233 Grs 0.055 0.052 0.063 - 0.055 0.071 0.060 0.061 0.056 Adr 0.m 0.010 0.000 0.000 0.000 0.000 0.001 0.003 Uva 0.W -dO.OOO 0.W 0.005 0.003 0.0 0.006 0.002 TabIe B34. Microprobe adyses of biotite fiom 28-886-2D.

Biotite 1 Biotite 2 Biotite 3 Averane core Rim Core Rim Core Rim Core &n Si02 36.52 37.28 37.42 36.81 36.94 36.72 36-96 36.94 Table B35. Microprobe analyses of chlorite from 28-886-2D.

Chlorite 1 Chlorite 2 Chlorite 3 Average Core Rim Core Rim Core Rim Core Rirn Si02 25.59 26.19 25.65 25.87 25.69 25.64 25.64 25.90 A1203 Ti02 Fe203 FeO MgO Mno cao Na20 no Cr203 H20

Stmctnral formulae: Si 2.634 w4) 1.366 Am 1.488 Ti 0.008 Fe3+ 0.000 Fe2+ 1.767 Mg 2.635 Mn 0.020 Ca 0.006 Na 0.000 K 0.016 Ct 0.000 0 10.000 OH 8.000 \ Table B36a. Microprobe analyses of pla&dase h28-886-2D.

A1203 Ti02 Fe203 FeO mo MnO cao Na20 no 0203 H20

Strucnual formulae: Si 2.060 M4) 1.907 W6) 0,000 Ti 0.000 Fe3+ 0.000 Fe2+ 0.013 Mg 0.000 Mn 0.000 Ca 0.973 Na 0.044 K 0.000 Cr 0.007 0 8.000 OH 0.000 \ Table B36b. Micropmbe analyses of planioclase from 28-886-2D.

6 7 8 9 10 Average Si02 44.53 A1203 Ti02 Fe203 FeO MI50 Mno CaO Na20 no Cr203 H20 Table 837. Microptobe analyses of stamlite fran 28-886-2Dwith ZnO.

Cote Rim Core Rirn Core Rim Core Rim Si02 28.70 29.86 28.34 29.22 2853 28.73 28.52 29.27 A1203 Ti02 Fe203 FeO MgO Milo can Na20 K20 zno H20 Table B38. Microprobe analyses of auddusite fkom 28-8862D.

1~ 2 3 4 5 6 Average Si02 36.99 35.47 35.85 36.17 35.53 36.03 36.01 A1203 Ti02 Fe203 FeO MgO MnO CaO Na20 no 0203

Stmcmral formulae: Si 1.024 0.963 AK4) 0.000 0.000 Al(6) 1.933 1.991 Ti 0.002 0.000 Fe3+ 0.042 0.007 Fe2+ 0.000 0.000 Mg 0.033 0.003 Mn 0.000 0.000 Ca 0.000 0.000 Na 0.000 0.000 K 0.000 0.000 Cr 0.000 0.000 0 5.000 5.000 Table B39. Microprobe adymofmaanetitc bm28-886-2D. Magnetite 1 2 3 4 5 6 7 Average Si02 0.80 0.63 0.78 0.86 0.80 0.90 0.66 0.78 A1203 Ti02 Fe203 FeO Mso MnO cao Na20 no Cr203

Structural fonnalae: Si 0.03 1 N4) 0.000 AIC6) 0.046 Ti 0.000 Fe3+ 1.882 Fe2+ 1.027 MI3 0.000 Mu 0.000 Ca 0.m Na 0.000 K 0.000 Cr 0.010 0 4.000